## Abstract

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.

References

[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)

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.

References

[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 language | English |
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State | Published - 1 Jul 2019 |

Event | European Conference on Nonlinear Optical Spectroscopy - Milan, Italy Duration: 6 Apr 2018 → … Conference number: 17 |

### Conference

Conference | European Conference on Nonlinear Optical Spectroscopy |
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Abbreviated title | ECONOS |

Country | Italy |

City | Milan |

Period | 6/04/18 → … |