Energy- and Frequency-Corrected Rotational Relaxation Matrix for Binary Collisions between Linear Molecules

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From the pioneering work of Anderson [1] on, a variety of fully quantum and semi-quantum versions of line
broadening theory has been elaborated that fostered progress in many spectroscopic applications (analysis of hot
gases, combustion, planetary atmospheres, etc). Yet, in these approaches collisions are treated as instantaneous
Markov events (scattering theory) whereas many well-known spectral signatures can be adequately interpreted
only when collisions are supposed to evolve within a finite duration. The relaxation matrix ᴦ, a fundamental
quantity of modern theory, then becomes dependent on frequency ω and its spectrum reflects the intracollisional
dynamics [2]. However, the computational complexity makes the ᴦ(ω)-matrix presently unattainable for direct
first-principle calculations and, hence, development of its simplified dynamically-based models has the pivotal
role for further progress.
So far, the ᴦ(ω) spectrum has been mimicked by two similar approaches, the frequency-extended, energycorrected sudden approximation (ECSA) [3] and the fast-collision model [4], which tackled the relaxation problem
of a linear rotator immersed into a monoatomic gas. Favourably, both models can be applied to arbitrary rotational
spectra, i.e., ones associated with molecular scalars (isotropic polarizability), vectors (dipoles) and tensors
(quadrupoles, etc) thus opening the way to multi-property fittings.
Here, extensions of these models to an important case of the nonMarkov collisions between two linear rotators
are reported. These approaches allow straightforward generalizations to similar collisions between any molecular
tops whose rotation is substantially slower than the relative translational motion.
[1] P. W. Anderson, "Pressure Broadening in the Microwave and Infra-Red Regions," Phys. Rev. 76, 647 (1949).
[2] U. Fano, "Pressure Broadening as a Prototype of Relaxation," Phys. Rev. 131, 259 (1963).
[3] J. V. Buldyreva and L. Bonamy, "Non-Markovian Energy-Corrected Sudden Model for the Rototranslational Spectrum of N2," Phys.
Rev. A 60, 370 (1999).
[4] A. Kouzov, "Rotational relaxation Matrix for Fast Non-Markovian Collisions," Phys. Rev. A 60, 2931 (1999)
Original languageEnglish
StatePublished - 1 Jul 2019
EventEuropean Conference on Nonlinear Optical Spectroscopy - Milan, Italy
Duration: 6 Apr 2018 → …
Conference number: 17


ConferenceEuropean Conference on Nonlinear Optical Spectroscopy
Abbreviated titleECONOS
Period6/04/18 → …

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