Showing papers on "Quadrupole published in 1995"
TL;DR: In this article, the relativistic pseudopotentials for the noble gases neon through xenon are presented together with corresponding optimized valence basis sets and used in calculations on the static dipole and quadrupole polarizabilities of the noble gas atoms.
Abstract: Nonrelativistic and one‐component relativistic energy‐adjusted ab initio pseudopotentials for the noble gases neon through xenon are presented together with corresponding optimized valence basis sets. To account for nonscalar relativistic effects the relativistic pseudopotentials are supplemented with effective spin–orbit potentials. The reliability of the presented pseudopotentials is demonstrated in atomic test calculations on ionization potentials and spin–orbit splittings in comparison with nonrelativistic and relativistic all‐electron calculations as well as experimental data. Together with extended valence basis sets the pseudopotentials are applied in calculations on the static dipole and quadrupole polarizabilities of the noble gas atoms. The best values, computed at the coupled‐cluster level of theory [CCSD(T)], for the dipole and quadrupole polarizabilities of the noble gases are 2.69a30 and 7.52a50 for Ne, 11.07a30 and 52.25a50 for Ar, 17.06a30 and 97.39a50 for Kr, and 27.66a30 and 209.85a50 fo...
443 citations
TL;DR: The 2PN terms, and in particular the finite mass contribution therein (which cannot be obtained in perturbation calculations of black hole spacetimes), are shown to make a significant contribution to the accumulated phase of theoretical templates to be used in matched filtering of the data from future gravitational-wave detectors.
Abstract: The rate of gravitational-wave energy loss from inspiralling binary systems of compact objects of arbitrary mass is derived through second post-Newtonian (2PN) order $O(({Gm/rc}^{2}{)}^{2})$ beyond the quadrupole approximation. The result has been derived by two independent calculations of the (source) multipole moments. The 2PN terms, and, in particular, the finite mass contribution therein (which cannot be obtained in perturbation calculations of black hole spacetimes), are shown to make a significant contribution to the accumulated phase of theoretical templates to be used in matched filtering of the data from future gravitational-wave detectors.
380 citations
329 citations
TL;DR: In this article, recent developments in the field of magnetic dipole excitations in heavy deformed nuclei are discussed by using electromagnetic and hadronic probes of different selectivity, with particular emphasis on the physics of the scissors mode and the spin magnetic dipoles giant resonance and the role neutrons and protons play in their description.
136 citations
TL;DR: In this article, the authors determined the quadrupole coupling constants for the deuteron and the oxygen nuclei in neat, liquid water by both theoretical and experimental methods, and reported the theoretical values of χD=264 kHz and χO=8.4 MHz.
Abstract: Quadrupole coupling constants, χQ, for the deuteron and the oxygen nuclei in neat, liquid water were determined by both theoretical and experimental methods. The theoretical values of χD=264 kHz and χO=8.4 MHz obtained from ab initio calculations at the MP2/6‐31+G* level in combination with a quantum cluster equilibrium model for liquids are in good agreement with results from NMR relaxation time experiments. Both theory and experiment show no observable temperature dependence of the quadrupole coupling constants. The theoretical values reported here for the oxygen quadrupole coupling constant and both the oxygen and deuterium asymmetry parameters are different from values obtained from ab initio calculations of clusters using molecular dynamics methods. This may be due to the use of pairwise additive potentials in the molecular dynamics simulations which do not take into account many‐body or polarizability effects.
126 citations
TL;DR: In this article, a number of low-J rotational transitions have been measured for two conformations of the simplest amino acid, glycine, providing precise hyperfine transition frequencies and electric dipole moments for radioastronomy searches for glycine in interstellar clouds.
Abstract: A number of low-J rotational transitions have been measured for two conformations of the simplest amino acid, glycine, providing precise hyperfine transition frequencies and electric dipole moments for radioastronomy searches for glycine in interstellar clouds. Measurements were made between 12 and 25 GHz with a pulsed-nozzle, Fabry-Perot-cavity, Fourier transform microwave spectrometer equipped with either a heated nozzle or laser ablation-nozzle for vaporization of solid phase glycine. Nuclear quadrupole coupling constants were determined for both conformers from measurements of the hyperfine-split rotational transitions. The quadrupole coupling constants for conformer I are eQqaa = -1.208(9) MHz and eQqbb = -0.343(8) MHz and for conformer II are eQqaa = 1.773(2) MHz and eQqbb = -3.194(4) MHz. The dipole moment components of both conformers were determined to higher precision. We obtain μa = 3.039(10) × 10-30 C m [0.911(3)D] and μb = 2.025(17) × 10-30 C m [0.607(5) D] for conformer I, and μa = 17.92(11) × 10-30 C m [5.372(34)D] and μb = 3.10(3) × 10-30 C m [0.93(1)D] for conformer II, where the uncertainties shown are 1 standard deviation.
116 citations
TL;DR: It is shown that the full information on the quantum state of the vibrational center-of-mass motion of a trapped ion can be transferred to its electronic dynamics by appropriately irradiating a long-living electronic transition by laser light.
Abstract: It is shown that the full information on the quantum state of the vibrational center-of-mass motion of a trapped ion can be transferred to its electronic dynamics by appropriately irradiating a long-living (e.g., quadrupole) electronic transition by laser light. This allows us to determine the quantum mechanical state of the ion with high quantum efficiency by probing a strong (dipole) transition for the appearance of resonance fluorescence.
113 citations
TL;DR: The purpose of this work is to show, on the basis of a particular effect related to the so-called gravitational-wave tail effect, that the observations of inspiralling compact binaries will permit also verification of some aspects of the nonlinear structure of general relativity.
Abstract: Future gravitational-wave experiments looking at inspiralling compact binaries could achieve the detection of a very small effect of phase modulation induced by the tails of gravitational waves. Once a binary signal has been identified, further analysis of data will provide a measure of the total mass-energy M of the binary, which enters as a factor in this tail effect, by means of optimal signal processing. The detection of the effect will then consist in showing the compatibility of the measured values of M and of the other parameters depending on the two masses of the binary. This illustrates the high potentiality of gravitational-wave experiments for testing general relativity. PACS numbers: 04.80.Nn, 04.30.Db, 97.60.Lf, 97.80.— d The first direct detection of gravitational radiation will probably take place in future gravitational-wave experiments such as LIGO and VIRGO. For the moment, the detection of gravitational radiation has only been indirect, thanks to the very precise timing observations of the binary pulsar 1913 + 16 [1]. Among the best candidate sources for a direct detection of gravitational radiation are binary systems of compact objects (neutron stars or black holes) in their late inspiralling stages of evolution [2]. The number of neutron-star coalescences is expected to be a few per year out to a distance of 100 Mpc [3] (with maybe a comparable number of black-hole coalescences), at which distance LIGO and VIRGO might observe the waves with a signal-to-noise ratio (SNR) — 10. Such a premiere will open a totally new field in astronomy, and will permit verification of some fundamental predictions of general relativity. Often quoted is the possibility of verifying that the waves are of pure helicity two, with no admixture of other spin states. The purpose of our work (this Letter and the detailed account [4]) is to show, on the basis of a particular effect related to the so-called gravitational-wave tail effect, that the observations of inspiralling compact binaries will permit also verification of some aspects of the nonlinear structure of general relativity. This verification is made possible by the now recognized fact [5] that a very precise general relativity prediction is needed to reach full potential accuracy on the measurement of the binary's parameters. The tail effect is essentially due to the propagation of gravitational radiation on the curved background spacetime generated by its own source. More specifically, the tail of the radiation results, at lowest order, from the nonlinear interaction between the time-varying quadrupole moment of the source (which generates the linear radiation) and its monopole moment, or total mass-energy M (which generates the background). The tail radiation has the distinctive property ("nonlocality" in time) of depending on the source's dynamics at arbitrary remote instants in the past, anterior to the simply retarded time t — r/c. This reflects the fact that gravity propagates not only on the light cone (direct propagation with the speed of light c), but also within the light cone (averaged propagation with all velocities less than c). (See [6] for references on tails and related nonlinear effects. ) The detection of the tail effect (or of effects immediately related to it) in future gravitational-wave experiments will provide direct evidence that gravity propagates on a curved space-time — that generated by its own source. (Note that indirect evidence from the observations of the binary pulsar is probably out of reach [6].) This will represent an interesting test of the nonlinearity of general relativity in the "gravitodynamics" regime of the theory, involving rapidly varying and strong gravitational fields. This will also provide an independent measurement of the total mass-energy M of the source. The tail effect arises at the so called 1 5 postNewtonian (1.5-PN) approximation in the radiation, i.e., at the relative order c 3 beyond the usual quadrupole radiation. Let us consider the radiation emitted by a general isolated source, at a large distance r from the source (neglecting terms that die out like 1/r~). More precisely, we denote by h(t) that linear combination of the components of the wave which is directly felt by some detector [e.g. , h(t) is the relative variation of the arm's length of a laser interferometric detector]. Then the expression of h(t), including all terms in the post-Newtonian expansion up to the order c, can be written [7] as
87 citations
TL;DR: The data were well reproduced by microscopic calculations using the same matter distribution used to explain the quadrupole moment data, and therefore provide new evidence for the existence of a proton halo in $^{8}\mathrm{B}$.
Abstract: Total reaction cross sections ${\mathrm{\ensuremath{\sigma}}}_{\mathit{R}}$ for $^{8}\mathrm{B}$, $^{12}\mathrm{C}$, and $^{14}\mathrm{N}$ on $^{\mathrm{nat}}\mathrm{Si}$ were measured from about 20 to 60 MeV/nucleon. The ${\mathrm{\ensuremath{\sigma}}}_{\mathit{R}}$ for $^{12}\mathrm{C}$ and $^{14}\mathrm{N}$ compared reasonably well with conventional strong absorption and microscopic calculations. Measured ${\mathrm{\ensuremath{\sigma}}}_{\mathit{R}}$ for $^{8}\mathrm{B}$ were slightly larger than those for the two heavier nuclei, and notably larger than the conventional calculations. The $^{8}\mathrm{B}$ data were well reproduced by microscopic calculations using the same matter distribution used to explain the $^{8}\mathrm{B}$ quadrupole moment data, and therefore provide new evidence for the existence of a proton halo in $^{8}\mathrm{B}$.
74 citations
TL;DR: In this article, the interaction of matter with light in the presence of a gravitational field is treated and it is shown that the electric dipole coupling remains unchanged provided the electric field as well as the dipole are operationally defined by measured quantities.
72 citations
TL;DR: The theory of the rotatory strength tensor describing circular dichroism (CD) of electronic excitations in oriented molecules is summarized in length and velocity formulations, and an ab initio implementation of the calculation of this tensor and its electric dipole and electric quadrupole components in the random phase approximation is presented in this article.
TL;DR: The S2 state electron paramagnetic resonance (EPR) multiline signal of Photosystem II has been simulated at Q-band, X-band and S-band frequencies, showing a high degree of anisotropy not expected in a d3 ion.
TL;DR: The structure of the HBr OCS van der Waals complex has been studied by Fourier transform microwave spectroscopy as mentioned in this paper, and the wide amplitude bending angle of the hydrogen bromide was calculated from the nuclear quadrupole coupling constant χaa to be 25.2°.
Abstract: The structure of the HBr OCS van der Waals complex has been studied by Fourier transform microwave spectroscopy. The ground state complex is hydrogen bound and quasilinear with SCO–HBr atomic ordering. Spectra from five different isotopomers were observed and assigned. The wide amplitude bending angle of the hydrogen bromide was calculated from the nuclear quadrupole coupling constant χaa to be 25.2°. Second order quadrupole effects, centrifugal distortion in the nuclear quadrupole coupling constant Dχ, a spin–rotation interaction, CBr, and a spin–spin interaction, Daa, were all included in the Hamiltonian. The following spectroscopic constants have been determined for the H79Br OCS isotopomer: B=488.7948(4) MHz; DJ=2.167(6) kHz; HJ=1.19(3) Hz; χaa=387.14(1) MHz; Dx=6.79(14) kHz; CBr=0.55(13) kHz; and Daa=7.7(1.2) kHz.
TL;DR: In this paper, a sum-rule method was applied to the data, the result of which implies that the vibrational quadrupole strengths of the 0 + and 4 + two-phonon states are fragmented and shared between several E2 matrix elements.
TL;DR: In this paper, the dipole and quadrupole moments of 17 small molecules, O2, NO, N2, CO, HF, HCl, N 2O, CO 2, OCS, CS2, NH3, C2H2, O3, SO2, H2O, H 2CO and C 2H2.
Abstract: An ab initio study of the dipole and quadrupole moments of 17 small molecules, O2, NO, N2, CO, HF, HCl, N2O, CO2, OCS, CS2, NH3, C2H2, O3, SO2, H2O, H2CO and C2H2, is reported. The moments are obtained as expectation values from multi-reference, configuration interaction wave functions corrected perturbatively by the so-called Bk procedure. All the wave functions employ the one-particle Gaussian basis sets of Sadlej that were specifically designed for the calculation of electric properties. The results are in generally good agreement with previous high-quality computations and experiment where available.
TL;DR: In this article, an electron spin echo envelope modulation (ESEEM) study was performed on the reduced primary electron-accepting ubiquinone-10 (Q A −• ) in Zn-substituted reaction centers of the photosynthetic bacterium Rhodobacter sphaeroides R26.
TL;DR: In this paper, the evolution of the magnetic field in white dwarfs with respect to the Hall effect has been investigated and it has been shown that in the presence of a strong (up to approximately 10(exp 9) G) internal toroidal magnetic field, even the lowest order poloidal modes can be substantially changed by the Hall effects.
Abstract: We calculate the evolution of the magnetic fields in white dwarfs, taking into account the Hall effect. Because this effect depends nonlinearly upon the magnetic field strength B, the time dependences of the various multipole field components are coupled. The evolution of the field is thus significantly more complicated than has been indicated by previous investigations. Our calculations employ recent white dwarf evolutionary sequences computed for stars with masses 0.4, 0.6, 0.8, and 1.0 solar mass. We show that in the presence of a strong (up to approximately 10(exp 9) G) internal toroidal magnetic field; the evolution of even the lowest order poloidal modes can be substantially changed by the Hall effect. As an example, we compute the evolution of an initially weak quadrupole component, which we take arbitrarily to be approximately 0.1%-1% of the strength of a dominant dipole field. We find that coupling provided by the Hall effect can produce growth of the ratio of the quadrupole to the dipole component of the surface value of the magnetic field strength by more than a factor of 10 over the 10(exp 9) to 10(exp 10) year cooling lifetime of the white dwarf. Some consequences of these results for the process of magnetic-field evolution in white dwarfs are briefly discussed.
TL;DR: In this article, the dynamics of collective motion in nuclei is described in the framework of time-dependent relativistic mean field theory for 16 O, 40 Ca, 48 Ca and compared with experimental data on energies and widths of giant resonances.
TL;DR: The combination of a quadrupoles lens and pulsed-ion injection may provide detection limits for the ICP-TOFMS that are competitive with those of quadrupole inductively coupled plasma-mass spectrometry instruments.
TL;DR: In this article, a molecular dynamics method was used to test the modern theory of the surface potential of polar liquid and to find out the dipole and quadrupole contribution to this potential.
Abstract: Clusters containing 64 molecules of water or bromine were investigated by the molecular dynamics method. Several water models and a bromine model were taken into consideration in order to test the modern theory of the surface potential of polar liquid and to find out the dipole and quadrupole contribution to this potential. The results of the simulations confirm strongly the theoretical conclusion that equally with the dipole contribution there is a purely quadrupolar contribution to the surface potential.
TL;DR: Shrinkage corrections of the microwave structures of H3NBF3 isotopomers resolve an apparent discrepancy between experimental and theoretical values of the NB bond length; ab initio 10B, 11B and 14N nuclear quadrupole coupling constants are in qualitative agreement with experiment, confirming the earlier microwave characterisation of this donor-acceptor adduct and providing a physical picture of dative bond formation as discussed by the authors.
Abstract: Shrinkage corrections of the microwave structures of H3NBF3 isotopomers resolve an apparent discrepancy between experimental and theoretical values of the NB bond length; ab initio10B, 11B and 14N nuclear quadrupole coupling constants are in qualitative agreement with experiment, confirming the earlier microwave characterisation of this donor–acceptor adduct and providing a physical picture of dative bond formation.
TL;DR: In this paper, the dipole moments have been estimated using the π 2π 2π pulse condition, and the corresponding quadrupole coupling constants have been derived for the rare gas dimers Ne-Kr and Ar−Kr.
Abstract: Pure rotational spectra of several isotopomeric species of the rare gas dimers Ne–Kr and Ar–Kr have been measured using a pulsed jet cavity microwave Fourier transform spectrometer. Equilibrium internuclear distances have been evaluated by taking advantage of the isotopic data, for both these dimers and three Xe‐containing dimers, whose spectra were reported earlier [Jager et al., J. Chem. Phys. 99, 919 (1993)]. The dipole moments have been estimated using the ‘‘π/2‐pulse’’ excitation condition. 83Kr nuclear quadrupole hyperfine structure has been observed in some rotational transitions of 20Ne–83Kr and of Ar–83Kr, and the corresponding quadrupole coupling constants have been derived.
TL;DR: In this paper, quadrupole coupling constants for deuterium and nitrogen nuclei are obtained for the sequence of linear (HCN)n clusters (up to n=6) at the RHF/6−31+G* level, complementing previous studies of ndependent "cooperative" effects in these C-H...N hydrogen-bonded species.
Abstract: Ab initio quadrupole coupling constants χ(D), χ(14N) for deuterium and nitrogen nuclei are obtained for the sequence of linear (HCN)n clusters (up to n=6) at the RHF/6‐31+G* level, complementing previous studies of n‐dependent ‘‘cooperative’’ effects in these C–H...N hydrogen‐bonded species. For the dimer and trimer, the theoretical values are compared with experimental equilibrium values of Gutowsky and co‐workers and found to successfully reproduce both the magnitudes and patterns of measured shifts. For larger (HCN)n clusters, the n‐dependent trends in χ(D), χ(14N) appear to be correlated with cooperativity effects found previously (binding energies, geometrical parameters, dipole moments, ir frequencies and intensities). This suggests that quadrupole coupling measurements can provide a useful probe of cooperative H‐bonding phenomena in gaseous and condensed media.
TL;DR: In this paper, the dynamics of solvation of the probe solute coumarin 153 have been measured with ~100 fs time resolution using the fluorescence upconversion technique.
16 May 1995
TL;DR: In this paper, the use of 14N signals in RDX and HMX has been investigated, where the principle is to subject the quadrupole nuclei to bursts of RF radiation and monitor the signals generated in the quiescent periods between pulses.
Abstract: Concerns the use of 14N signals in RDX and HMX. The principle is to subject the quadrupole nuclei to bursts of RF radiation and monitor the signals generated in the quiescent periods between pulses. These signals may be divided into two types: free induction decays (FID) and echoes. The first is the decaying signal observed immediately following the pulse; it is generated by the interaction of the oscillating magnetic field B of the applied RF with the magnetic moment of the quadrupolar nucleus. Often, this B field is generated by surrounding the sample with a small induction coil; the pulse may be imagined to tip the nuclear quadrupole moments away from their equilibrium orientation in the electric field gradient of their surroundings by a so-called "flip" angle α; they then precess at one of their allowed frequencies inducing a voltage in the same RF coil used to excite the transition. This voltage is observed to decay with a time constant, the FID or spin phase memory decay time. In many solids there are variations in the quadrupole frequencies due, for example, to defects or impurities in the material which alter the electric field gradient in their vicinity. The result is to produce a de-phasing of the NQR precession frequencies and a decay of the RF signal. Practical equipment is developed.
TL;DR: In this paper, a pulse electron nuclear double resonance method is proposed that correlates the hyperfine splittings to the nuclear transition frequencies in a two-dimensional experiment, and the theoretical predictions are confirmed by experiments on a single crystal and on a spin-label-doped polymer.
TL;DR: In this article, the quadrupole and octupole correlations in 194Pb were investigated by means of the generator coordinate method, and static microscopic wave functions were obtained by constrained Hartree-Fock+BCS calculations using the effective interaction SkM∗.
TL;DR: In this article, the quadrupolar hard dumbbell model has been determined by Monte Carlo simulation for several values of quadrupole moment and molecular elongation, and the model gives a qualitatively correct description of trends in the solid-fluid equilibrium.
Abstract: Solid–fluid equilibrium for the quadrupolar hard dumbbell model has been determined by Monte Carlo simulation for several values of the quadrupole moment and molecular elongation. Several solid structures have been studied including α‐N2, a fcc plastic crystal, based centered monoclinic structure providing closest packing for hard dumbbells and two orthorhombic structures. For low elongations, hard dumbbells freeze into a plastic crystal phase when the quadrupole moment is low and into the α‐N2 structure when it is large. More elongated dumbbells freeze into a close‐packed structure for low quadrupole moment, into an orthorhombic structure for moderate quadrupole moment and into the α‐N2 structure for large quadrupole moment. For any elongation and quadrupole moment the stable phase at very high pressures is one of the close‐packed structures. The quadrupolar hard dumbbell model gives a qualitatively correct description of trends in the solid–fluid equilibrium for several systems including N2, the halogen...
TL;DR: In this paper, the authors developed the theory needed to calculate nuclear quadrupole splittings without defining an inertial axis system for the complex and applied it to Ar-CO2, Ar-HCl and Ar-N2 as test cases.
Abstract: The nuclear quadrupole coupling constants of van der Waals complexes contain valuable information on intermolecular forces. In the past, the coupling constants have been interpreted in terms of angular expectation values, involving the projections of the monomer coupling constant onto the inertial axes of the complex. However, this is a significant approximation. The present paper develops the theory needed to calculate nuclear quadrupole splittings without defining an inertial axis system for the complex. The theory is applied to Ar-CO2, Ar-HCl and Ar-N2 as test cases. An improved value of the quadrupole coupling constant of the N2 monomer is obtained, based on the microwave spectra of Ar-N2 and Kr-N2.