Rotational State-to-State Transition Rate Coefficients for H2O + H2O Collisions at Nonequilibrium Conditions

Document Type

Article

Publication Date

8-2024

Publisher

EDP Sciences

Source Publication

Astronomy & Astrophysics

Source ISSN

0004-6361

Original Item ID

DOI: 10.1051/0004-6361/202450738

Abstract

Aims. The goal is to develop a database of rate coefficients for rotational state-to-state transitions in H2O + H2O collisions that is suitable for the modeling of energy transfer in nonequilibrium conditions, in which the distribution of rotational states of H2O deviates from local thermodynamic equilibrium.

Methods. A two-temperature model was employed that assumed that although there is no equilibrium between all possible degrees of freedom in the system, the translational and rotational degrees of freedom can be expected to achieve their own equilibria independently, and that they can be approximately characterized by Boltzmann distributions at two different temperatures, Tkin and Trot.

Results. Upon introducing our new parameterization of the collisional rates, taking into account their dependence on both Tkin and Trot, we find a change of up to 20% in the H2O rotational level populations for both ortho and para-H2O for the part of the cometary coma where the nonequilibrium regime occurs.

Comments

Astronomy & Astrophysics, Vol. 688 (August 2024).

DOI.

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Link to Full Text

Share

COinS