Absorption (logic)

About: Absorption (logic) is a research topic. Over the lifetime, 5733 publications have been published within this topic receiving 236302 citations.

Study of the Interaction of Light with Rough Metal Surfaces. I. Experiment

Abstract: This paper describes measurements of the reflectivity, scattering, and transmission of light by metals with rough surfaces. For surfaces whose roughness is very short ranged, the ratio of rough-surface reflectivity to smooth-surface reflectivity varies exponentially as ${\ensuremath{\lambda}}^{\ensuremath{-}2}$ both above the plasmon frequency and in regions where ${\ensuremath{\epsilon}}_{2}\ensuremath{\gg}|{\ensuremath{\epsilon}}_{1}|$. In the latter regions for these rough surfaces, the scattered intensity follows a ${\ensuremath{\lambda}}^{\ensuremath{-}4}$ wavelength variation. For surfaces which are more wavy, the reflectivity and scattered light vary less rapidly with wavelength. Well below the plasmon frequency, additional fields not present on smooth surfaces, but coming from induced extra currents and dipoles on rough surfaces, add coherently to the specular beam, with a resonant wavelength variation. Near the plasmon frequency there is extra absorption. We have studied the angular variation of the scattered light, and have observed additional incoherent light associated with these extra dipoles and currents. We compare the experimental results with the scalar scattering theory and make some general comments about the properties of surface dipoles and currents.

Theory of nonlinear oscillating dipolar excitations in one-dimensional condensates

Abstract: We find that for a one-dimensional condensate in the presence of an applied ac field, a significant absorption peak should occur for values of the external frequency just below the pinning frequency ${\ensuremath{\omega}}_{F}$. This power absorption is due to those nonlinear normal modes of the condensate known as "breathers," which are shown to phase lock with the applied field.

Pinning and conductivity of two-dimensional charge-density waves in magnetic fields

Abstract: The dynamical properties of the impurity pinning of phasons of the charge-density wave are investigated for two-dimensional electron systems in the presence of magnetic fields applied perpendicular to the system. The effect of magnetic fields is treated classically. It is found that there exists a finite size of domains if the impurity potential overwhelms the long-range part of mutual Coulomb interactions, and the magnetoconductivity tensor is evaluated in such cases. The cyclotron resonance is shown to be shifted and broadened. It is predicted that absorption of electromagnetic waves exists at the pinned-mode frequency though the oscillator strength will be smaller by a factor of ${({\ensuremath{\omega}}_{c}\ensuremath{\tau})}^{\ensuremath{-}2}$ than the cyclotron resonance if ${\ensuremath{\omega}}_{c}\ensuremath{\tau}\ensuremath{\gg}1$, where ${\ensuremath{\omega}}_{c}$ and $\ensuremath{\tau}$ are the cyclotron frequency and the damping of the resonance, respectively.

A High-Resolution Hubble Space Telescope Study of Apparent Lyman Continuum Leakers at $z\sim3$

Abstract: We present $U_{336}V_{606}J_{125}H_{160}$ follow-up $HST$ observations of 16 $z\sim3$ candidate LyC emitters in the HS1549+1919 field. With these data, we obtain high spatial-resolution photometric redshifts of all sub-arcsecond components of the LyC candidates in order to eliminate foreground contamination and identify robust candidates for leaking LyC emission. Of the 16 candidates, we find one object with a robust LyC detection that is not due to foreground contamination. This object (MD5) resolves into two components; we refer to the LyC-emitting component as MD5b. MD5b has an observed 1500\AA\ to 900\AA\ flux-density ratio of $(F_{UV}/F_{LyC})_{obs}=4.0\pm2.0$, compatible with predictions from stellar population synthesis models. Assuming minimal IGM absorption, this ratio corresponds to a relative (absolute) escape fraction of $f_{esc,rel}^{MD5b}=75-100$% ($f_{esc,abs}^{MD5b}=14-19$%). The stellar population fit to MD5b indicates an age of $\lesssim50$Myr, which is in the youngest 10% of the $HST$ sample and the youngest third of typical $z\sim3$ Lyman break galaxies, and may be a contributing factor to its LyC detection. We obtain a revised, contamination-free estimate for the comoving specific ionizing emissivity at $z=2.85$, indicating (with large uncertainties) that star-forming galaxies provide roughly the same contribution as QSOs to the ionizing background at this redshift. Our results show that foreground contamination prevents ground-based LyC studies from obtaining a full understanding of LyC emission from $z\sim3$ star-forming galaxies. Future progress in direct LyC searches is contingent upon the elimination of foreground contaminants through high spatial-resolution observations, and upon acquisition of sufficiently deep LyC imaging to probe ionizing radiation in high-redshift galaxies.

Neutrino Transport in Strongly Magnetized Proto-Neutron Stars and the Origin of Pulsar Kicks: The Effect of Asymmetric Magnetic Field Topology

Abstract: In proto-neutron stars with strong magnetic fields, the cross section for νe (${u{{ν}}{"7016}}$ --> -->e) absorption on neutrons (protons) depends on the local magnetic field strength resulting from the quantization of energy levels for the e- (e+) produced in the final state. If the neutron star possesses an asymmetric magnetic field topology in the sense that the magnitude of magnetic field in the north pole is different from that in the south pole, then asymmetric neutrino emission may be generated. We calculate the absorption cross sections of νe and ${u{{ν}}{"7016}}$ --> -->e in strong magnetic fields as a function of the neutrino energy. These cross sections exhibit oscillatory behaviors that occur because new Landau levels for the e- (e+) become accessible as the neutrino energy increases. By evaluating the appropriately averaged neutrino opacities, we demonstrate that the change in the local neutrino flux caused by the modified opacities is rather small. To generate appreciable kick velocity (~300 km s-1) to the newly formed neutron star, the difference between the field strengths at the two opposite poles of the star must be at least 1016 G. We also consider the magnetic field effect on the spectral neutrino energy fluxes. The oscillatory features in the absorption opacities give rise to modulations in the emergent spectra of νe and ${u{{ν}}{"7016}}$ --> -->e.