N. Egorova - Academia.edu (original) (raw)

Papers by N. Egorova

AIP Conference Proceedings, 2008

Exact and general analytic expressions are reported for the integrated intensity and the width of... more Exact and general analytic expressions are reported for the integrated intensity and the width of collision-induced absorption (CIA) and collision-induced scattering (CIS) bands by gases of centrosymmetric linear molecules. These expressions provide significant insight and allow assignment of partial second moments to the degrees of freedom of the colliding molecules. The expressions are applied to ambient CO 2 , whose collisional spectra are reputed to be useful probes for terrestrial and planetary atmospheres. Compelling evidence of the substantial role of hitherto missing polarization and polarizability mechanisms is provided and is in remarkable agreement with experimental observation. Our findings allow the long-overdue simple interpretation of CIA and CIS by CO 2 -CO 2 without the need to resort to short-range interactions to offset the discrepancies between theory and experiment.

Physical Review A, 2006

Page 1. Collision-induced spectroscopy with long-range intermolecular interactions: A diagrammati... more Page 1. Collision-induced spectroscopy with long-range intermolecular interactions: A diagrammatic representation and the invariant form of the induced properties AP Kouzov* Institute of Physics, Saint Petersburg State University, Ulyanovskaya str. ...

Physical Review A, 2007

ABSTRACT We report an exhaustive joint theoretical/experimental collision-induced Raman scatterin... more ABSTRACT We report an exhaustive joint theoretical/experimental collision-induced Raman scattering (CIRS) study of the Raman-forbidden nu3 band of CO2 . Original zeroth and second anisotropic spectral moment formulas for CO2-Ar are derived, in which complete expressions of Raman amplitudes (derived by the authors with a recently reported universal method [Phys. Rev. A 74, 012723 (2006)]) are input. The method, applicable to any kind of spectroscopy and whatever the number of photons, molecules, or interaction involved, uses the irreducible spherical tensor formalism in conjunction with a Feynman-like diagrammatic technique to describe any long-range induced property mechanism. Experimentally, spectral moments are deduced from careful, absolute-scale, frequency-resolved CO2-Ar depolarized CIRS measurements of unprecedented accuracy. From comparison between theory and experiment, we provide quantitative evidence of a substantial contribution of a nonlinear dipole polarization mechanism, predicted theoretically in the preceding paper. In this mechanism, both photons are shown to interact with Ar (which then couples to CO2 via intermolecular interactions), rather than with both colliders that is the case in the standard dipole-induced quadrupole (DIQ) interaction. The effect had thus far escaped notice possibly because of the reduced accuracy of the earlier self-consistent field dipole-quadrupole polarizablity computations along with a lack of CIRS measurements. In light of recent extensive computations by Haskopoulos and Maroulis [Chem. Phys. Lett. 417, 235 (2006)], the improved ab initio data of these properties are found to corroborate our predictions, and confirm that the Raman amplitude owing to the dipole-dipole-quadrupole hyperpolarizability of the atomic perturber strongly and destructively interferes with the (otherwise dominant) DIQ Raman amplitude.

Journal of Raman Spectroscopy, 2005

Two-photon transition amplitudes, accounting for virtual double electric dipole-electric quadrupo... more Two-photon transition amplitudes, accounting for virtual double electric dipole-electric quadrupole (E1, E2) and electric dipole-magnetic dipole (E1, M1) transitions, are derived for isotropic molecular ensembles. The new-type non-resonant Raman scattering is shown to appear from the interfering emission fields generated by multipoles (electric dipole, electric quadrupole and magnetic dipole) induced on a scattering particle. The interference is found to affect strongly the angular distribution and polarization characteristics of the scattered radiation, damping the forward scattering while enhancing the backward scattering. When the excitation frequency approaches an absorption resonance, the interference features are shown to disappear from the Raman spectra. In the off-resonance case, the Raman cross-section equations for gases of linear and spherical (T d ) molecules are elaborated in terms of the mixed electronic polarizabilities expressed via their invariants in the molecule-fixed frame.

AIP Conference Proceedings, 2008

Exact and general analytic expressions are reported for the integrated intensity and the width of... more Exact and general analytic expressions are reported for the integrated intensity and the width of collision-induced absorption (CIA) and collision-induced scattering (CIS) bands by gases of centrosymmetric linear molecules. These expressions provide significant insight and allow assignment of partial second moments to the degrees of freedom of the colliding molecules. The expressions are applied to ambient CO 2 , whose collisional spectra are reputed to be useful probes for terrestrial and planetary atmospheres. Compelling evidence of the substantial role of hitherto missing polarization and polarizability mechanisms is provided and is in remarkable agreement with experimental observation. Our findings allow the long-overdue simple interpretation of CIA and CIS by CO 2 -CO 2 without the need to resort to short-range interactions to offset the discrepancies between theory and experiment.

Physical Review A, 2006

Page 1. Collision-induced spectroscopy with long-range intermolecular interactions: A diagrammati... more Page 1. Collision-induced spectroscopy with long-range intermolecular interactions: A diagrammatic representation and the invariant form of the induced properties AP Kouzov* Institute of Physics, Saint Petersburg State University, Ulyanovskaya str. ...

Physical Review A, 2007

ABSTRACT We report an exhaustive joint theoretical/experimental collision-induced Raman scatterin... more ABSTRACT We report an exhaustive joint theoretical/experimental collision-induced Raman scattering (CIRS) study of the Raman-forbidden nu3 band of CO2 . Original zeroth and second anisotropic spectral moment formulas for CO2-Ar are derived, in which complete expressions of Raman amplitudes (derived by the authors with a recently reported universal method [Phys. Rev. A 74, 012723 (2006)]) are input. The method, applicable to any kind of spectroscopy and whatever the number of photons, molecules, or interaction involved, uses the irreducible spherical tensor formalism in conjunction with a Feynman-like diagrammatic technique to describe any long-range induced property mechanism. Experimentally, spectral moments are deduced from careful, absolute-scale, frequency-resolved CO2-Ar depolarized CIRS measurements of unprecedented accuracy. From comparison between theory and experiment, we provide quantitative evidence of a substantial contribution of a nonlinear dipole polarization mechanism, predicted theoretically in the preceding paper. In this mechanism, both photons are shown to interact with Ar (which then couples to CO2 via intermolecular interactions), rather than with both colliders that is the case in the standard dipole-induced quadrupole (DIQ) interaction. The effect had thus far escaped notice possibly because of the reduced accuracy of the earlier self-consistent field dipole-quadrupole polarizablity computations along with a lack of CIRS measurements. In light of recent extensive computations by Haskopoulos and Maroulis [Chem. Phys. Lett. 417, 235 (2006)], the improved ab initio data of these properties are found to corroborate our predictions, and confirm that the Raman amplitude owing to the dipole-dipole-quadrupole hyperpolarizability of the atomic perturber strongly and destructively interferes with the (otherwise dominant) DIQ Raman amplitude.

Journal of Raman Spectroscopy, 2005

Two-photon transition amplitudes, accounting for virtual double electric dipole-electric quadrupo... more Two-photon transition amplitudes, accounting for virtual double electric dipole-electric quadrupole (E1, E2) and electric dipole-magnetic dipole (E1, M1) transitions, are derived for isotropic molecular ensembles. The new-type non-resonant Raman scattering is shown to appear from the interfering emission fields generated by multipoles (electric dipole, electric quadrupole and magnetic dipole) induced on a scattering particle. The interference is found to affect strongly the angular distribution and polarization characteristics of the scattered radiation, damping the forward scattering while enhancing the backward scattering. When the excitation frequency approaches an absorption resonance, the interference features are shown to disappear from the Raman spectra. In the off-resonance case, the Raman cross-section equations for gases of linear and spherical (T d ) molecules are elaborated in terms of the mixed electronic polarizabilities expressed via their invariants in the molecule-fixed frame.