Showing papers on "Absorption (logic) published in 2020"

Constraints on low-mass, relic dark matter candidates from a surface-operated SuperCDMS single-charge sensitive detector

Abstract: This article presents an analysis and the resulting limits on light dark matter inelastically scattering off of electrons, and on dark photon and axion-like particle absorption, using a second-generation SuperCDMS high-voltage eV-resolution detector. The 0.93 gram Si detector achieved a 3 eV phonon energy resolution; for a detector bias of 100 V, this corresponds to a charge resolution of 3% of a single electron-hole pair. The energy spectrum is reported from a blind analysis with 1.2 gram-days of exposure acquired in an above-ground laboratory. With charge carrier trapping and impact ionization effects incorporated into the dark matter signal models, the dark matter-electron cross section $\bar{\sigma}_{e}$ is constrained for dark matter masses from 0.5--$10^{4} $MeV$/c^{2}$; in the mass range from 1.2--50 eV$/c^{2}$ the dark photon kinetic mixing parameter $\varepsilon$ and the axioelectric coupling constant $g_{ae}$ are constrained. The minimum 90% confidence-level upper limits within the above mentioned mass ranges are $\bar{\sigma}_{e}\,=\,8.7\times10^{-34}$ cm$^{2}$, $\varepsilon\,=\,3.3\times10^{-14}$, and $g_{ae}\,=\,1.0\times10^{-9}$.

FRB Periodicity: Mild Pulsars in Tight O/B-star Binaries

Abstract: Periodicities observed in two Fast Radio Burst (FRB) sources (16 days in FRB 180916.J0158+65 and 160 days in FRB 121102) are consistent with that of tight, stellar mass binary systems. In the case of FRB 180916.J0158+65 the primary is an early OB-type star with mass loss rate $\dot{M} \sim 10^{-8}- 10^{-7} M_\odot$ yr$^{-1}$, and the secondary a neutron star. The observed periodicity is not intrinsic to the FRB's source, but is due to the orbital phase-dependent modulation of the absorption conditions in the massive star's wind. The observed relatively narrow FRB activity window implies that the primary's wind dynamically dominates that of the pulsar, $\eta = L_{sd}/(\dot{M} v_w c) \leq 1$, where $L_{sd} $ is pulsar spin-down, $\dot{M}$ is the primary's wind mass loss rate and $v_w$ is its velocity. The condition $\eta \leq 1$ requires mildly powerful pulsar with $L_{sd} \lesssim 10^{37}$ erg $s^{-1}$. The observations are consistent with magnetically-powered radio emission originating in the magnetospheres of strongly magnetized neutron stars, the classical magnetars.

A Significantly Neutral Intergalactic Medium Around the Luminous z = 7 Quasar J0252–0503

Abstract: Luminous $z\ge7$ quasars provide direct probes of the evolution of supermassive black holes (SMBHs) and the intergalactic medium (IGM) during the epoch of reionization (EoR). The Ly$\alpha$ damping wing absorption imprinted by neutral hydrogen in the IGM can be detected in a single EoR quasar spectrum, allowing the measurement of the IGM neutral fraction towards that line of sight. However, damping wing features have only been detected in two $z>7$ quasars in previous studies. In this paper, we present new high quality optical and near-infrared spectroscopy of the $z=7.00$ quasar DES J025216.64--050331.8 obtained with Keck/NIRES and Gemini/GMOS. By using the MgII single-epoch virial method, we find that it hosts a $\rm (1.39\pm0.16) \times10^{9} ~M_\odot$ SMBH accreting at an Eddington ratio of $\lambda_{\rm Edd}=0.7\pm0.1$, consistent with the values seen in other luminous $z\sim 7$ quasars. Furthermore, the Ly$\alpha$ region of the spectrum exhibits a strong damping wing absorption feature. The lack of associated metal absorption in the quasar spectrum indicates that this absorption is imprinted by a neutral IGM. Using a state-of-the-art model developed by Davies et al., we measure a volume-averaged neutral hydrogen fraction at $z=7$ of $\langle x_{\rm HI} \rangle = 0.70^{+0.20}_{-0.23} (^{+0.28}_{-0.48})$ within 68% (95%) confidence intervals when marginalizing over quasar lifetimes of $10^3\le t_{\rm Q}\le10^8$ yr. This is the highest IGM neutral fraction yet measured using reionization-era quasar spectra.

New limits on dark photons from solar emission and keV scale dark matter

Abstract: We provide updates to the limits on solar emission of dark photons or more generally, any light vector particle coupled to the electron vector current. The recent 2019 and 2020 electronic recoil data from XENON1T now provide more stringent constraints on these models than the stellar energy loss in the sub-keV mass region. We also show that solar emission of dark photons does not provide a good fit to the recent XENON1T excess in the 2--5 keV energy bins. In contrast, the absorption of 2--4 keV mass dark photons that saturate the local dark matter mass density does provide a good fit to the excess, for mixing angles in the range $\ensuremath{\epsilon}\ensuremath{\in}(4--12)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$, while satisfying astrophysical constraints. Similarly, other models utilizing the vector portal can fit the excess, including those with operators that directly couple the dark photon field strength to electron spin.

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) III. Atmospheric structure of the misaligned ultra-hot Jupiter WASP-121b

Abstract: Ultra-hot Jupiters offer interesting prospects for expanding our theories on dynamical evolution and the properties of extremely irradiated atmospheres. In this context, we present the analysis of new optical spectroscopy for the transiting ultra-hot Jupiter WASP-121b. We first refine the orbital properties of WASP-121b, which is on a nearly polar (obliquity $\psi^{\rm North}$=88.1$\pm$0.25$^{\circ}$ or $\psi^{\rm South}$=91.11$\pm$0.20$^{\circ}$) orbit, and exclude a high differential rotation for its fast-rotating (P$<$1.13 days), highly inclined ($i_\mathrm{\star}^{\rm North}$=8.1$\stackrel{+3.0}{_{-2.6}}^{\circ}$ or $i_\mathrm{\star}^{\rm South}$=171.9$\stackrel{+2.5}{_{-3.4}}^{\circ}$) star. We then present a new method that exploits the reloaded Rossiter-McLaughlin technique to separate the contribution of the planetary atmosphere and of the spectrum of the stellar surface along the transit chord. Its application to HARPS transit spectroscopy of WASP-121b reveals the absorption signature from metals, likely atomic iron, in the planet atmospheric limb. The width of the signal (14.3$\pm$1.2 km/s) can be explained by the rotation of the tidally locked planet. Its blueshift (-5.2$\pm$0.5 km/s) could trace strong winds from the dayside to the nightside, or the anisotropic expansion of the planetary thermosphere.

Mass loss rate and local thermodynamic state of KELT-9 b thermosphere from the hydrogen Balmer series

Abstract: KELT-9 b, the hottest known exoplanet with $T\sim4400$ K, is the archetype of a new planet class known as ultra-hot Jupiters. These exoplanets are presumed to have an atmosphere dominated by neutral and ionized atomic species. In particular, H$\alpha$ and H$\beta$ Balmer lines have been detected in the KELT-9 b upper atmosphere, suggesting that hydrogen is filling the planetary Roche lobe and escaping from the planet. In this work, we detected $\delta$ Scuti-type stellar pulsation (with a period $P=7.54\pm0.12$ h) and studied the Rossiter-McLaughlin effect (finding a spin-orbit angle $\lambda=-85.01^°\pm0.23^°$) prior to focussing on the Balmer lines (H$\alpha$ to H$\zeta$) in the optical transmission spectrum of KELT-9 b. Our HARPS-N data show significant absorption for H$\alpha$ to H$\delta$. The precise line shapes of the H$\alpha$, H$\beta$, and H$\gamma$ absorptions allow us to put constraints on the thermospheric temperature. Moreover, the mass loss rate, and the excited hydrogen population of KELT-9 b are also constrained, thanks to a retrieval analysis performed with a new atmospheric model. We retrieved a thermospheric temperature of $T=13200^{+800}_{-720}$ K and a mass loss rate of $\dot{M}=10^{12.8\pm0.3}$ g s$^{-1}$ when the atmosphere was assumed to be in hydrodynamical expansion and in local thermodynamic equilibrium (LTE). Since the thermospheres of hot Jupiters are not expected to be in LTE, we explored atmospheric structures with non-Boltzmann equilibrium for the population of the excited hydrogen. We do not find strong statistical evidence in favor of a departure from LTE. However, our non-LTE scenario suggests that a departure from the Boltzmann equilibrium may not be sufficient to explain the retrieved low number densities of the excited hydrogen. In non-LTE, Saha equilibrium departure via photo-ionization, is also likely to be necessary to explain the data.

A He I upper atmosphere around the warm Neptune GJ 3470b

Abstract: High resolution transit spectroscopy has proven to be a reliable technique for the characterization of the chemical composition of exoplanet atmospheres. Taking advantage of the broad spectral coverage of the CARMENES spectrograph, we initiated a survey aimed at characterizing a broad range of planetary systems. Here, we report our observations of three transits of \tplanet with CARMENES in search of \het\ absorption. On one of the nights, the He~{\sc i} region was heavily contaminated by OH$^-$ telluric emission and, thus, it was not useful for our purposes. The remaining two nights had a very different signal-to-noise ratio (S/N) due to weather. They both indicate the presence of \het\ absorption in the transmission spectrum of \tplanet, although a statistically valid detection can only be claimed for the night with higher S/N. For that night, we retrieved a 1.5$\pm$0.3\% absorption depth, translating into a $R_p(\lambda)/R_p = 1.15\pm 0.14$ at this wavelength. Spectro-photometric light curves for this same night also indicate the presence of extra absorption during the planetary transit with a consistent absorption depth. The \het\ absorption is modeled in detail using a radiative transfer code, and the results of our modeling efforts are compared to the observations. We find that the mass-loss rate, \mlr, is confined to a range of 3\,$\times\,10^{10}$\,\gs\ for $T$ = 6000\,K to 10\,$\times\,10^{10}$\,\gs\ for $T$ = 9000\,K. We discuss the physical mechanisms and implications of the He~{\sc i} detection in \tplanet and put it in context as compared to similar detections and non-detections in other Neptune-size planets. We also present improved stellar and planetary parameter determinations based on our visible and near-infrared observations.

The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Baryon acoustic oscillations with Lyman-$\alpha$ forests

Abstract: We present a measurement of baryonic acoustic oscillations (BAO) from Lyman-$\alpha$ (Ly$\alpha$) absorption and quasars at an effective redshift $z=2.33$ using the complete extended Baryonic Oscillation Spectroscopic Survey (eBOSS). The sixteenth and final eBOSS data release (SDSS DR16) contains all data from eBOSS and its predecessor, the Baryonic Oscillation Spectroscopic Survey (BOSS), providing $210,005$ quasars with $z_{q}>2.10$ that are used to measure Ly$\alpha$ absorption. We measure the BAO scale both in the auto-correlation of Ly$\alpha$ absorption and in its cross correlation with $341,468$ quasars with redshift $z_{q}>1.77$. Apart from the statistical gain from new quasars and deeper observations, the main improvements over previous work come from more accurate modeling of physical and instrumental correlations and the use of new sets of mock data. Combining the BAO measurement from the auto- and cross-correlation yields the constraints of the two ratios $D_{H}(z=2.33)/r_{d} = 8.99 \pm 0.19$ and $D_{M}(z=2.33)/r_{d} = 37.5 \pm 1.1$, where the error bars are statistical. These results are within $1.5\sigma$ of the prediction of the flat-$\Lambda$CDM cosmology of Planck~(2016). The analysis code, \texttt{picca}, the catalog of the flux-transmission field measurements, and the $\Delta \chi^{2}$ surfaces are publicly available.

MHz laser absorption spectroscopy via diplexed RF modulation for pressure, temperature, and species in rotating detonation rocket flows

Abstract: A mid-infrared laser absorption sensing method has been developed to quantify gas properties (temperature, pressure, and species density) at MHz measurement rates, with application to annular rotating detonation rocket flows. Bias-tee circuitry is integrated with distributed feedback quantum cascade and interband cascade lasers in the $$4{-}5~\mu \hbox {m}$$ range enabling diplexed radio frequency (RF) wavelength modulation on the order of several MHz while yielding sufficient scan depth to capture multiple rovibrational transitions in the fundamental vibrational bands of $${\text {CO}}$$ and $${\text {CO}}_{2}$$ . Sub-microsecond spectrally-resolved $${\text {CO}}$$ absorption lineshapes provide for inference of temperature and species from a two-line area ratio and pressure from collision line-width. $${\text {CO}}_{2}$$ column density is inferred from peak-to-valley differential absorption at the bandhead near $$4.19~\mu \hbox {m}$$ . A field demonstration on a methane-oxygen rotating detonation rocket engine was performed utilizing an in situ single-ended retro-reflection optical configuration aligned at the exhaust plane. The target gas properties are temporally-resolved at up to 3 MHz across rotating detonations with up to 20 kHz cycle frequency.

Phy-X/ZeXTRa: a software for robust calculation of effective atomic numbers for photon, electron, proton, alpha particle, and carbon ion interactions

Abstract: The purpose of the present work is robust calculation of effective atomic numbers ($${Z}_{\text{eff}}$$s) for photon, electron, proton, alpha particle and carbon ion interactions through the newly developed software, Phy-X/ZeXTRa (Zeff of materials for X-Type Radiation attenuation). A pool of total mass attenuation and energy absorption coefficients (for photons) and total mass stopping powers (for charged particles) for elements was constructed first. Then, a matrix of interaction cross sections for elements Z = 1–92 was constructed. Finally, effective atomic numbers were calculated for any material by interpolating adjacent cross sections through a linear logarithmic interpolation formula. The results for $${Z}_{\text{eff}}$$ for photon interaction were compared with those calculated through Mayneord’s formula, which suggests a single-valued $${Z}_{\text{eff}}$$ for any material for low-energy photons for which photoelectric absorption is the dominant interaction process. The single-valued $${Z}_{\text{eff}}$$ was found to agree well with that obtained by other methods, in the low-energy region. In addition, $${Z}_{\text{eff}}$$ values of various materials of biological interest were compared with those obtained experimentally at 59.54 keV. In general, the agreement between values calculated with Phy-X/ZeXTRa and Auto-Zeff and those measured were satisfactory. A comparison of $${Z}_{\text{eff}}$$ values for photon energy absorption calculated with Phy-X/ZeXTRa and literature values for a nucleotide base, adenine, was made, and the relative difference (RD) in $${Z}_{\text{eff}}$$ between Phy-X/ZeXTRa and literature values was found to be 2% < RD < 11%, at low photon energies (1–100 keV), while it was less than 1% at energies higher than 100 keV. Highest $${Z}_{\text{eff}}$$ values were observed at low photon energies, where photoelectric absorption dominates photon interaction. For electrons, corresponding RD(%) values in $${Z}_{\text{eff}}$$ were found to be in the range 0.4 ≤ RD(%) ≤ 1.7, while for heavy charged particle interactions it was 2.4 ≤ RD(%) ≤ 4.2 for total proton interaction and 0 ≤ RD(%) ≤ 8 for total alpha particle interaction. In view of the importance of $${Z}_{\text{eff}}$$ for identifying and differentiating tissues in diagnostic imaging as well as for estimating accurate dose in radiotherapy and particle-beam therapy, Phy-X/ZeXTRa could be used for fast and accurate calculation of $${Z}_{\text{eff}}$$ in a wide energy range for both photon and charged particle (electrons, protons, alpha particles and C ions) interactions.

Ab Initio Studies of Exciton g Factors: Monolayer Transition Metal Dichalcogenides in Magnetic Fields

Abstract: The effect of a magnetic field on the optical absorption in semiconductors has been measured experimentally and modeled theoretically for various systems in previous decades. We present a new first-principles approach to systematically determine the response of excitons to magnetic fields, i.e., exciton $g$ factors. By utilizing the $GW$-Bethe-Salpeter equation methodology we show that $g$ factors extracted from the Zeeman shift of electronic bands are strongly renormalized by many-body effects which we trace back to the extent of the excitons in reciprocal space. We apply our approach to monolayers of transition metal dichalcogenides (${\mathrm{MoS}}_{2}$, ${\mathrm{MoSe}}_{2}$, ${\mathrm{MoTe}}_{2}$, ${\mathrm{WS}}_{2}$, and ${\mathrm{WSe}}_{2}$) with strongly bound excitons for which $g$ factors are weakened by about 30%.

Microwave electrometry via electromagnetically induced absorption in cold Rydberg atoms

Abstract: The atom-based traceable standard for microwave electrometry shows promising advantages by enabling stable and uniform measurement. Here we theoretically propose and then experimentally realize an alternative direct International System of Units (SI)--traceable and self-calibrated method for measuring a microwave-electric-field strength based on electromagnetically induced absorption (EIA) in cold Rydberg atoms. Comparing with the method of electromagnetically induced transparency, we show that the equivalence relation between the microwave Rabi frequency and Autler-Townes splitting is more valid and is even more robust against the experimental parameters in the EIA's linear region. Furthermore, a narrower linewidth of cold Rydberg EIA enables us to realize a direct SI-traceable microwave-electric-field measurement as small as $\ensuremath{\sim}100\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{V}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$.

Massive warm/hot galaxy coronae - II. Isentropic model

Abstract: We construct a new analytic phenomenological model for the extended circumgalactic material (CGM) of $L^*$ galaxies. Our model reproduces the OVII/OVIII absorption observations of the Milky Way (MW) and the OVI measurements reported by the COS-Halos and eCGM surveys. The warm/hot gas is in hydrostatic equilibrium in a MW gravitational potential, and we adopt a barotropic equation of state, resulting in a temperature variation as a function of radius. A pressure component with an adiabatic index of $\gamma=4/3$ is included to approximate the effects of a magnetic field and cosmic rays. We introduce a metallicity gradient motivated by the enrichment of the inner CGM by the Galaxy. We then present our fiducial model for the corona, tuned to reproduce the observed OVI-OVIII column densities, and with a total mass of $M_{\rm gas} \approx 5.5 \times 10^{10}~{\rm M_{\odot}}$ inside $r_{\rm cgm} \approx 280$ kpc. The gas densities in the CGM are low ($n_{\rm H} = 10^{-5} - 3 \times 10^{-4}~{\rm cm^{-3}}$) and its collisional ionization state is modified by the metagalactic radiation field (MGRF). We show that for OVI-bearing warm/hot gas with typical observed column densities $N_{\rm OVI} \sim 3 \times 10^{14}~{\rm cm^{-2}}$ at large ($\gtrsim 100$ kpc) impact parameters from the central galaxies, the ratio of the cooling to dynamical times, $t_{\rm cool}/t_{\rm dyn}$, has a model-independent upper limit of $\lesssim 4$. In our model, $t_{\rm cool}/t_{\rm dyn}$ at large radii is $\sim 2-3$. We present predictions for a wide range of future observations of the warm/hot CGM, from UV/X-ray absorption and emission spectroscopy, to dispersion measure (DM) and Sunyaev-Zeldovich CMB measurements. We provide the model outputs in machine-readable data files, for easy comparison and analysis.

Energy-Coupling Mechanisms Revealed through Simultaneous Keyhole Depth and Absorptance Measurements during Laser-Metal Processing

Abstract: The interaction between high-irradiance light and molten metal is the complex multiphysics phenomenon that underpins industrial processes such as laser-based additive manufacturing, welding, and cutting. One aspect that requires careful attention is the formation and evolution of vapor depressions, or keyholes, within the molten metal. The dynamic behavior of these depressions can dramatically change the number of laser-beam reflections and is therefore intrinsically linked to the instantaneous energy coupled into the system. Despite its importance, there is a severe lack of direct in situ, experimental evidence of this relationship, which creates challenges for those who aim to model or control laser-based manufacturing processes. In this work, we combine two simultaneous state-of-the-art real-time measurement techniques (inline coherent imaging and integrating-sphere radiometry) to confirm and explore the definite positive correlation between the highly dynamic vapor-depression geometry and laser energy absorptance. For irradiances resulting in vapor-depression formation ($\ensuremath{\ge}0.49\phantom{\rule{0.1em}{0ex}}{\mathrm{MW}/\mathrm{cm}}^{2}$), we observe excellent correlation (0.86) between the instantaneous depth (down to 800 $\ensuremath{\mu}\mathrm{m}$) and the absorptance (up to 0.92), directly demonstrating their interdependence. In the transition mode, an important regime for additive manufacturing, we observe temporary vapor-depression formation with concomitant changes in absorptance from 0.34 to 0.53. At higher irradiances, we detect stepwise increases in the absorbed laser power with a smoothly increasing keyhole depth, which is a real-time experimental observation of the effect of multiple reflections during laser-metal processing. The value of simultaneous depth and absorption measurements for predictive model validation is presented using ray-tracing simulations, which also confirm the absorption enhancement via incremental increases in the reflection count. This work provides insight into the underlying physics of laser-based metal manufacturing that is useful toward deterministic modeling and real-time process control.

Oxygenation of monolayer gallium monochalcogenides: Design of two-dimensional ternary Ga 2 X O structures (X =S ,Se ,Te )

Abstract: The possibility of breaking structural symmetry with realization of Janus monolayers offers new possibilities in the field of two-dimensional (2D) materials, and various ternary systems including the class of group-III monochalcogenides have been suggested. However, interaction of oxygen was shown to modify optoelectronic properties of gallium monochalcogenides, and design of ternary systems with oxygen as a third component has not been considered yet. In this paper, we design and investigate 2D ${\mathrm{Ga}}_{2}X\text{O}$ ($X=\mathrm{S},\mathrm{Se},\mathrm{Te}$) systems by using first-principles calculations. Phonon spectra analysis and molecular dynamics simulations indicate that while ${\mathrm{Ga}}_{2}\mathrm{SO}$ and ${\mathrm{Ga}}_{2}\mathrm{SeO}$ are stable even at high temperatures ${\mathrm{Ga}}_{2}\mathrm{TeO}$ is dynamically unstable. Inclusion of oxygen makes ${\mathrm{Ga}}_{2}\mathrm{SO}$ and ${\mathrm{Ga}}_{2}\mathrm{SeO}$ less brittle when compared to their binary constituents. While $\mathrm{Ga}X$ monolayers have indirect band gaps, ${\mathrm{Ga}}_{2}\mathrm{SO}$ and ${\mathrm{Ga}}_{2}\mathrm{SeO}$ become direct band-gap semiconductors and the band gap can be further tuned by tensile/compressive strain. Additionally, depending on the type of the system, strong optical absorption within the infrared, visible, and/or ultraviolet region is also predicted. Finally, structural and electronic properties of bilayers of ${\mathrm{Ga}}_{2}X\text{O}$ are examined and compared with monolayers. Our results not only predict stable 2D ternary ${\mathrm{Ga}}_{2}X\text{O}$ structures but also suggest them as promising materials for optoelectronic applications.

Dark trions govern the temperature-dependent optical absorption and emission of doped atomically thin semiconductors

Abstract: We perform absorption and photoluminescence spectroscopy of trions in hBN-encapsulated $\mathrm{WS}{\mathrm{e}}_{2}$, ${\mathrm{WS}}_{2},\phantom{\rule{0.28em}{0ex}}\mathrm{MoS}{\mathrm{e}}_{2}$, and $\mathrm{Mo}{\mathrm{S}}_{2}$ monolayers, depending on temperature. The different trends for W- and Mo-based materials are excellently reproduced considering a Fermi-Dirac distribution of bright and dark trions. We find a dark trion, ${X}_{\mathrm{D}}^{\ensuremath{-}}$, 19 meV below the lowest bright trion, ${X}_{1}^{\ensuremath{-}}$, in $\mathrm{WS}{\mathrm{e}}_{2}$ and $\mathrm{W}{\mathrm{S}}_{2}$. In $\mathrm{MoS}{\mathrm{e}}_{2}$, ${X}_{\mathrm{D}}^{\ensuremath{-}}$ lies 6 meV above ${X}_{1}^{\ensuremath{-}}$, while ${X}_{\mathrm{D}}^{\ensuremath{-}}$ and ${X}_{1}^{\ensuremath{-}}$ almost coincide in $\mathrm{Mo}{\mathrm{S}}_{2}$. Our results agree with GW-Bethe-Salpeter equation (GW-BSE) ab initio calculations and quantitatively explain the optical response of doped monolayers with temperature.

The Impact of New d(p,\gamma)He3 Rates on Big Bang Nucleosynthesis

Abstract: We consider the effect on Big Bang Nucleosynthesis (BBN) of new measurements of the $d(p,\gamma){}^3$He cross section by the LUNA Collaboration. These have an important effect on the primordial abundance of D/H which is also sensitive to the baryon density at the time of BBN. We have re-evaluated the thermal rate for this reaction, using a world average of cross section data, which we describe with model-independent polynomials; our results are in good agreement with a similar analysis by LUNA. We then perform a full likelihood analysis combining BBN and Planck cosmic microwave background (CMB) likelihood chains using the new rate combined with previous measurements and compare with the results using previous rates. Concordance between BBN and CMB measurements of the anisotropy spectrum using the old rates was excellent. The predicted deuterium abundance at the Planck value of the baryon density was $({\rm D/H})_{\rm BBN+CMB}^{\rm old} = (2.57 \pm 0.13) \times 10^{-5}$ which can be compared with the value determined from quasar absorption systems $({\rm D/H})_{\rm obs} = (2.55 \pm 0.03) \times 10^{-5} $. Using the new rates we find $({\rm D/H})_{\rm BBN+CMB} = (2.51 \pm 0.11) \times 10^{-5}$. We thus find consistency among BBN theory, deuterium and ${}^4$He observations, and the CMB, when using reaction rates fit in our data-driven approach. We also find that the new reaction data tightens the constraints on the number of relativistic degrees of freedom during BBN, giving the effective number of light neutrino species $N_ u = 2.880 \pm 0.144$ in good agreement with the Standard Model of particle physics. Finally, we note that the observed deuterium abundance continues to be more precise than the BBN+CMB prediction, whose error budget is now dominated by $d(d,n){}^3$He and $d(d,p){}^{3}{\rm H}$.

A new era of fine structure constant measurements at high redshift

Abstract: New observations of the quasar HE0515$-$4414 have been made using the HARPS spectrograph on the ESO 3.6m telescope, aided by the Laser Frequency Comb (LFC). We present three important advances for $\alpha$ measurements in quasar absorption spectra from these observations. Firstly, the data have been wavelength calibrated using LFC and ThAr methods. The LFC wavelength calibration residuals are six times smaller than when using the standard ThAr calibration. We give a direct comparison between $\alpha$ measurements made using the two methods. Secondly, spectral modelling was performed using Artificial Intelligence (fully automated, all human bias eliminated), including a temperature parameter for each absorption component. Thirdly, in contrast to previous work, additional model parameters were assigned to measure $\alpha$ for each individual absorption component. The increase in statistical uncertainty from the larger number of model parameters is small and the method allows a substantial advantage; outliers that would otherwise contribute a significant systematic, possibly corrupting the entire measurement, are identified and removed, permitting a more robust overall result. The $z_{abs} = 1.15$ absorption system along the HE0515$-$4414 sightline yields 40 new $\alpha$ measurements. We constrain spatial fluctuations in $\alpha$ to be $\Delta\alpha/\alpha \leq 9 \times 10^{-5}$ on scales $\approx 20\;{\rm km\,s}^{-1}$, corresponding to $\approx25\;$kpc if the $z_{abs} = 1.15$ system arises in a $1\;$Mpc cluster. Collectively, the 40 measurements yield $\Delta\alpha/\alpha=-0.27\pm2.41\times10^{-6}$, consistent with no variation.

MIR-Pump NIR-Probe Fiber-Optic Photothermal Spectroscopy With Background-Free First Harmonic Detection

Abstract: We demonstrated MIR-pump NIR-probe photothermal spectroscopy with the first harmonic (PTS- $1{f}$ ) detection of formaldehyde, one of the most common volatile organic compounds (VOCs), in a silica hollow-core negative curvature fiber (HC-NCF). The photothermal gas sensor adopts a mid-infrared interband cascade pump laser at $3.6~\mu \text{m}$ and a near-infrared fiber probe laser at $1.56~\mu \text{m}$ . At the optimal modulation frequency (8 kHz) and modulation index (1.8) of the pump laser, we obtained a normalized noise equivalent absorption (NNEA) coefficient of $4\times 10^{-9}$ cm−1WHz $^{-1/2}$ . The use of HC-NCF with an inner diameter of $65~\mu \text{m}$ enables the sensitive photothermal detection even for a very low pump power of micro-watts. The background-free PTS- $1{f}$ detection was observed to enhance the sensitivity by a factor of 2.4 compared to the second harmonic ( $2{f}$ ) detection. A theoretical model was established in this work to interpret the experimental results.

X-ray observations of luminous dusty quasars at z > 2

Abstract: We present new X-ray observations of luminous heavily dust-reddened quasars (HRQs) selected from infrared sky surveys. HRQs appear to be a dominant population at high redshifts and the highest luminosities, and may be associated with a transitional "blowout" phase of black hole and galaxy co-evolution models. Despite this, their high-energy properties have been poorly known. We use the overall sample of $10$ objects with XMM-Newton coverage to study the high-energy properties of HRQs at $\left = 10^{47.5}$ erg/s and $\left = 2.5$. For the seven sources with strong X-ray detections, we perform spectral analyses. These find a median X-ray luminosity of $\left = 10^{45.1}$ erg/s, comparable to the most powerful X-ray quasars known. The gas column densities are $N_{\rm H}=(1$-$8)\times 10^{22}$ cm$^{-2}$, in agreement with the amount of dust extinction observed. The dust to gas ratios are sub-Galactic, but are higher than found in local AGN. The intrinsic X-ray luminosities of HRQs are weak compared to the mid-infrared ($L_{\rm 6\mu m}$) and bolometric luminosities ($L_{\rm bol}$), in agreement with findings for other luminous quasar samples. For instance, the X-ray to bolometric corrections range from $\kappa_{\rm bol}\approx 50$-$3000$. The moderate absorption levels and accretion rates close to the Eddington limit ($\left =1.06$) are in agreement with a quasar blowout phase. Indeed, we find that the HRQs lie in the forbidden region of the $N_{\rm H}$-$\lambda_{\rm Edd}$ plane, and therefore that radiation pressure feedback on the dusty interstellar medium may be driving a phase of blowout that has been ongoing for a few $10^{5}$ years. The wider properties, including [OIII] narrow-line region kinematics, broadly agree with this interpretation.

The warm-hot circumgalactic medium around EAGLE-simulation galaxies and its detection prospects with X-ray and UV line absorption

Abstract: We use the EAGLE (Evolution and Assembly of GaLaxies and their Environments) cosmological simulation to study the distribution of baryons, and far-ultraviolet (O VI), extreme-ultraviolet (Ne VIII) and X-ray (O VII, O VIII, Ne IX, and Fe XVII) line absorbers, around galaxies and haloes of mass $\mathrm{M}_{200c}=10^{11}$-$10^{145}\,\mathrm{M}_{\odot}$ at redshift 01 EAGLE predicts that the circumgalactic medium (CGM) contains more metals than the interstellar medium across halo masses The ions we study here trace the warm-hot, volume-filling phase of the CGM, but are biased towards temperatures corresponding to the collisional ionization peak for each ion, and towards high metallicities Gas well within the virial radius is mostly collisionally ionized, but around and beyond this radius, and for O VI, photoionization becomes significant When presenting observables we work with column densities, but quantify their relation with equivalent widths by analysing virtual spectra Virial-temperature collisional ionization equilibrium ion fractions are good predictors of column density trends with halo mass, but underestimate the diversity of ions in haloes Halo gas dominates the highest column density absorption for X-ray lines, but lower density gas contributes to strong UV absorption lines from O VI and Ne VIII Of the O VII (O VIII) absorbers detectable in an Athena X-IFU blind survey, we find that 41 (56) per cent arise from haloes with $\mathrm{M}_{200c}=10^{120}$-$10^{135}\,\mathrm{M}_{\odot}$ We predict that the X-IFU will detect O VII (O VIII) in 77 (46) per cent of the sightlines passing $\mathrm{M}_{\star}=10^{105}$-$10^{110}\,\mathrm{M}_{\odot}$ galaxies within 100 pkpc (59 (82) per cent for $\mathrm{M}_{\star}>10^{110}\,\mathrm{M}_{\odot}$) Hence, the X-IFU will probe covering fractions comparable to those detected with the Cosmic Origins Spectrograph for O VI

Nuclear Excitation of the ^{229}Th Isomer via Defect States in Doped Crystals.

Abstract: When Th nuclei are doped in ${\mathrm{CaF}}_{2}$ crystals, a set of electronic defect states appear in the crystal band gap which would otherwise provide complete transparency to vacuum-ultraviolet radiation. The coupling of these defect states to the 8 eV $^{229m}\mathrm{Th}$ nuclear isomer in the ${\mathrm{CaF}}_{2}$ crystal is investigated theoretically. We show that although previously viewed as a nuisance, the defect states provide a starting point for nuclear excitation via electronic bridge mechanisms involving stimulated emission or absorption using an optical laser. The rates of these processes are at least 2 orders of magnitude larger than direct photoexcitation of the isomeric state using available light sources. The nuclear isomer population can also undergo quenching when triggered by the reverse mechanism, leading to a fast and controlled decay via the electronic shell. These findings are relevant for a possible solid-state nuclear clock based on the $^{229m}\mathrm{Th}$ isomeric transition.

Frame-independent spatial coordinate z ∼: Implications for light-front wave functions, deep inelastic scattering, light-front holography, and lattice QCD calculations

Abstract: A general procedure for obtaining frame-independent three-dimensional light-front coordinate-space wave functions is introduced. The third spatial coordinate $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{z}$ is the boost and Lorentz frame-independent coordinate conjugate to the light-front momentum coordinate $x=\frac{{k}^{+}}{{P}^{+}}$ which appears in the momentum-space light-front wave functions underlying generalized parton distributions, structure functions, distribution amplitudes, form factors, and other hadronic observables. These causal light-front coordinate-space wave functions are used to derive a general expression for the quark distribution function of hadrons as an integral over the frame-independent longitudinal distance (the Ioffe time) between virtual-photon absorption and emission appearing in the forward virtual photon-hadron Compton scattering amplitude. Specific examples using models derived from light-front holographic QCD show that the spatial extent of the proton eigenfunction in the longitudinal direction can have a very large extent in $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{z}$.

Detection of the hydrogen Balmer lines in the ultra-hot Jupiter WASP-33b

Abstract: Ultra-hot Jupiters (UHJs) are highly irradiated giant exoplanets with extremely high day-side temperatures, which lead to thermal dissociation of most of the molecular species. It is expected that the neutral hydrogen atom is one of the main species in the upper atmospheres of ultra-hot Jupiters. Neutral hydrogen has been detected in several UHJs by observing its Balmer line absorption. Here, we report four transit observations of the ultra-hot Jupiter WASP-33b, performed with the CARMENES and HARPS-North spectrographs, and the detection of the H${\alpha}$, H${\beta}$, and H${\gamma}$ lines in the planetary transmission spectrum. The combined H$\alpha$ transmission spectrum of the four transits has an absorption depth of 0.99$\pm$0.05 %, which corresponds to an effective radius of 1.31$\pm$0.01 Rp . The strong H${\alpha}$ absorption indicates that the line probes the high-altitude thermosphere. We further fitted the three Balmer lines using the PAWN model, assuming that the atmosphere is hydrodynamic and in LTE. We retrieved a thermosphere temperature $12200^{+1300}_{-1000}$ K and a mass-loss rate ${\rm \dot{M}}=10^{11.8^{+0.6}_{-0.5}}$ g/s. The retrieved large mass-loss rate is compatible with the "Balmer-driven" atmospheric escape scenario, in which the stellar Balmer continua radiation in the near-ultraviolet is substantially absorbed by the excited hydrogen atoms in the planetary thermosphere.

MusE GAs FLOw and Wind (MEGAFLOW) IV. A two sightline tomography of a galactic wind

Abstract: Galactic outflows are thought to eject baryons back out to the circum-galactic medium (CGM). Studies based on metal absorption lines (MgII in particular) in the spectra of background quasars indicate that the gas is ejected anisotropically, with galactic winds likely leaving the host in a bi-conical flow perpendicular to the galaxy disk. In this paper, we present a detailed analysis of an outflow from a z = 0.7 "green-valley" galaxy (log($M_*$/$\mathrm{M}_\odot$) = 9.9; SFR = 0.5 $\mathrm{M}_\odot\,\mathrm{yr}^{-1}$) probed by two background sources part of the MUSE Gas Flow and Wind (MEGAFLOW) survey. Thanks to a fortuitous configuration with a background quasar (SDSSJ1358+1145) and a bright background galaxy at $z = 1.4$, both at impact parameters of $\approx 15\,\mathrm{kpc}$, we can - for the first time - probe both the receding and approaching components of a putative galactic outflow around a distant galaxy. We measure a significant velocity shift between the MgII absorption from the two sightlines ($84\pm17\,\mathrm{km}\,\mathrm{s}^{-1}$), which is consistent with the expectation from our simple fiducial wind model, possibly combined with an extended disk contribution.

Atomic processes of shear-coupled migration in { 112 } twins and vicinal grain boundaries in bcc-Fe

Abstract: Tilt ${112}$ grain boundaries (GBs) in bcc metals perform shear-coupled grain-boundary migration by the creation and glide of disconnections. Disconnection dipoles may be created at the pristine GB at high stresses or may be generated at the core of a GB dislocation that acts as a source of disconnections. We characterize this source in terms of its Burgers vector, denoted ${\stackrel{P\vec}{b}}_{1/\ensuremath{-}1}$, and describe the mechanism that allows the source to move conservatively with the GB. The ${\stackrel{P\vec}{b}}_{1/\ensuremath{-}1}$ grain-boundary dislocation is created, for instance, during the absorption of a crystal dislocation by the ${112}$ grain boundary. In addition, ${\stackrel{P\vec}{b}}_{1/\ensuremath{-}1}$ accommodates ${112}$ vicinal grain boundaries that are formed by segments of ${112}$ planes separated by ${\stackrel{P\vec}{b}}_{1/\ensuremath{-}1}$ grain-boundary dislocations. The presence of these ${\stackrel{P\vec}{b}}_{1/\ensuremath{-}1}$ dislocations facilitates the conservative displacement of both the pristine and the vicinal GBs. We show that the creation of disconnections is the key for the absorption of edge and screw dislocations by the GB and the drag of mixed dislocations by the GB during its migration. These conservative processes are efficient ways to accommodate plastic deformation by the growth and shrink of ${112}$ twins, and shear-coupled motion of the ${112}$ GB and its vicinal GBs.

The AARTFAAC Cosmic Explorer: observations of the 21-cm power spectrum in the EDGES absorption trough

Abstract: The 21-cm absorption feature reported by the EDGES collaboration is several times stronger than that predicted by traditional astrophysical models. If genuine, a deeper absorption may lead to stronger fluctuations on the 21-cm signal on degree scales (up to 1~Kelvin in rms), allowing these fluctuations to be detectable in nearly 50~times shorter integration times compared to previous predictions. We commenced the "AARTFAAC Cosmic Explorer" (ACE) program, that employs the AARTFAAC wide-field imager, to measure or set limits on the power spectrum of the 21-cm fluctuations in the redshift range $z = 17.9-18.6$ ($\Delta u = 72.36-75.09$~MHz) corresponding to the deep part of the EDGES absorption feature. Here, we present first results from two LST bins: 23.5-23.75h and 23.5-23.75h, each with 2~h of data, recorded in `semi drift-scan' mode. We demonstrate the application of the new ACE data-processing pipeline (adapted from the LOFAR-EoR pipeline) on the AARTFAAC data. We observe that noise estimates from the channel and time-differenced Stokes~$V$ visibilities agree with each other. After 2~h of integration and subtraction of bright foregrounds, we obtain $2\sigma$ upper limits on the 21-cm power spectrum of $\Delta_{21}^2 < (8139~\textrm{mK})^2$ and $\Delta_{21}^2 < (8549~\textrm{mK})^2$ at $k = 0.144~h\,\textrm{cMpc}^{-1}$ for the two LST bins. Incoherently averaging the noise bias-corrected power spectra for the two LST bins yields an upper limit of $\Delta_{21}^2 < (7388~\textrm{mK})^2$ at $k = 0.144~h\,\textrm{cMpc}^{-1}$. These are the deepest upper limits thus far at these redshifts.

Strain-engineered widely tunable perfect absorption angle in black phosphorus from first principles

Abstract: Using the density functional theory of electronic structure, we compute the anisotropic dielectric response of bulk black phosphorus subject to strain. Employing the obtained permittivity tensor, we solve Maxwell's equations and study the electromagnetic response of a layered structure comprising a film of black phosphorus stacked on a metallic substrate. Our results reveal that a small compressive or tensile strain, $\ensuremath{\approx}4%$, exerted either perpendicular or in the plane to the black phosphorus growth direction, efficiently controls the epsilon-near-zero response and allows perfect absorption tuning from low angle of the incident beam $\ensuremath{\theta}={0}^{\ensuremath{\circ}}$ to high values $\ensuremath{\theta}\ensuremath{\approx}{90}^{\ensuremath{\circ}}$ while switching the energy flow direction. Incorporating the spatially inhomogeneous strain model, we also find that for certain thicknesses of the black phosphorus, near-perfect absorption can be achieved through controlled variations of the in-plane strain. These findings can serve as guidelines for designing largely tunable perfect electromagnetic wave absorber devices.

A third-order nonlinear optical single crystal of 3,4-dimethoxy-substituted chalcone derivative with high laser damage threshold value: a potential material for optical power limiting

Abstract: Third-order nonlinear optical material 4-[(1E)-3-(3,4-dimethoxyphenyl)-3-oxoprop-1-en-1-yl]phenyl 4-methylbenzene-1-sulfonate (DMPMS) is crystallized by slow solvent evaporation technique. The crystal has inversion symmetry and belongs to monoclinic system with $${P2}_{1}/c$$ space group. The C–H⋯O/C–H⋯π intermolecular interactions will be large complementarity for molecular density/crystal packing. A comprehensive investigation for absorbance and emission properties has been performed. Thermal stability is up to 258 °C without any weight loss and calculated value of laser damage threshold is ≈ 12 GW/cm2. The DMPMS shows low dielectric constant value, about 4.42 at 1 MHz and electronic polarizability values in the order of $${10}^{-23}$$ cm3. Furthermore, theoretical calculation has been performed using B3LYP and M06-2X functional. The static first-order hyperpolarizability parameter is 55 (B3LYP) and 34 (M06-2X) times that of urea. The total contribution of second-order hyperpolarizability is − 37.9 $$\times {10}^{-40 }\mathrm{esu}$$ (in B3LYP functional) and − 25.77 $$\times {10}^{-40 }\mathrm{esu}$$ (in M06-2X functional), respectively. Here, two-photon absorption mechanism is responsible for nonlinear absorption and co-efficient is found to be $$28.3 \times {10}^{-12}$$ m/W. In optical limiting study, limiting threshold is found to be 65 µJ. The real and imaginary third-order nonlinear optical susceptibility is of the order $${10}^{-12} \mathrm{esu}$$ .

On the Benefits of Populations for the Exploitation Speed of Standard Steady-State Genetic Algorithms

Abstract: It is generally accepted that populations are useful for the global exploration of multi-modal optimisation problems. Indeed, several theoretical results are available showing such advantages over single-trajectory search heuristics. In this paper we provide evidence that evolving populations via crossover and mutation may also benefit the optimisation time for hillclimbing unimodal functions. In particular, we prove bounds on the expected runtime of the standard ( $$\mu +1$$ ) GA for OneMax that are lower than its unary black box complexity and decrease in the leading constant with the population size up to $$\mu =o\left( \sqrt{\log n}\right) $$ . Our analysis suggests that the optimal mutation strategy is to flip two bits most of the time. To achieve the results we provide two interesting contributions to the theory of randomised search heuristics: (1) A novel application of drift analysis which compares absorption times of different Markov chains without defining an explicit potential function. (2) The inversion of fundamental matrices to calculate the absorption times of the Markov chains. The latter strategy was previously proposed in the literature but to the best of our knowledge this is the first time is has been used to show non-trivial bounds on expected runtimes.