## Abstract

Higher accuracy of spectroscopic data modeling of different gaseous media is urgently called by progress in

atmospheric physics and gas diagnostics. This task demands development of flexible theoretical models

applicable to different processes induced by collisional relaxation. Such flexibility is inherent to the energycorrected sudden approximation (ECSA) introduced almost 40 years ago [1] but still retaining its popularity for

fittings of congested spectral structures near the band centers. Its extended variants [2,3] are able to tackle the

non-Markovian collisional relaxation of arbitrary rank up to the far spectral wings but apply strictly to the

single case of linear rotators perturbed by structureless particles. Here, we report rigorous non-Markovian

ECSA relaxation matrix expressions obtained for collisions between pairs of linear molecules.

For that, the ECSA scattering operators and the intermolecular potential W are expanded in series of scalar

tripolar spherical harmonics [4] whose arguments are orientations of three axes, two of the linear colliders and

the third one of the intermolecular separation. All relaxation characteristics can be obtained when the Fouriertransforms of the ECSA time correlation functions are known. These transforms can be either calculated from

first principles or modeled using a priori information and accounting for the fundamental properties of the

relaxation matrix. Besides, the ECSA spectral functions can be mimicked in terms of the leading spectral

moments which are readily obtained from the tripolar expansions of W and of the binary distribution function.

The presented approach allows straightforward generalizations to collisions between any molecular tops whose

rotation is substantially slower than the relative translational motion.

References:

[1] A.E. De Pristo, S.D. Augustin, R. Ramaswamy, and H. Rabitz, J. Chem. Phys. 71, 850 (1979) .

[2] A. Kouzov, Phys. Rev.A 60, 2931 (1999).

[3] J.V. Buldyreva and L. Bonamy, Phys. Rev.A 60, 370 (1999).

[4] D. A. Varshalovich, A. N. Moskalev, and V. K. Khersonskii, Quantum Theory of Angular Momentum (World

Scientific, Singapore, 1988)

atmospheric physics and gas diagnostics. This task demands development of flexible theoretical models

applicable to different processes induced by collisional relaxation. Such flexibility is inherent to the energycorrected sudden approximation (ECSA) introduced almost 40 years ago [1] but still retaining its popularity for

fittings of congested spectral structures near the band centers. Its extended variants [2,3] are able to tackle the

non-Markovian collisional relaxation of arbitrary rank up to the far spectral wings but apply strictly to the

single case of linear rotators perturbed by structureless particles. Here, we report rigorous non-Markovian

ECSA relaxation matrix expressions obtained for collisions between pairs of linear molecules.

For that, the ECSA scattering operators and the intermolecular potential W are expanded in series of scalar

tripolar spherical harmonics [4] whose arguments are orientations of three axes, two of the linear colliders and

the third one of the intermolecular separation. All relaxation characteristics can be obtained when the Fouriertransforms of the ECSA time correlation functions are known. These transforms can be either calculated from

first principles or modeled using a priori information and accounting for the fundamental properties of the

relaxation matrix. Besides, the ECSA spectral functions can be mimicked in terms of the leading spectral

moments which are readily obtained from the tripolar expansions of W and of the binary distribution function.

The presented approach allows straightforward generalizations to collisions between any molecular tops whose

rotation is substantially slower than the relative translational motion.

References:

[1] A.E. De Pristo, S.D. Augustin, R. Ramaswamy, and H. Rabitz, J. Chem. Phys. 71, 850 (1979) .

[2] A. Kouzov, Phys. Rev.A 60, 2931 (1999).

[3] J.V. Buldyreva and L. Bonamy, Phys. Rev.A 60, 370 (1999).

[4] D. A. Varshalovich, A. N. Moskalev, and V. K. Khersonskii, Quantum Theory of Angular Momentum (World

Scientific, Singapore, 1988)

Original language | English |
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Pages | 64-64 |

Number of pages | 1 |

State | Published - 20 Aug 2017 |

Event | The 25th Colloquium on High-Resolution Molecular Spectroscopy - Helsinki, Finland Duration: 20 Aug 2017 → 25 Aug 2017 |

### Conference

Conference | The 25th Colloquium on High-Resolution Molecular Spectroscopy |
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Country | Finland |

City | Helsinki |

Period | 20/08/17 → 25/08/17 |