Chapter 5
Energy Transfer in Collisions
Abstract Inelastic collision processes, namely, processes of energy exchange of
translational motion (T-T exchange), a transformation of translational, and rotational energy (R-T exchange), a transformation of vibrational energy (V-T, V-R and
V-V exchange) are discussed briefly. Then perturbation-facilitated and
perturbation-irrelevant collision-induced non-adiabatic transitions (CINATs), and
other processes in which CINATs occur, are considered. CINATs between halogen
ion-pair states are examined in detail.
We are starting to discuss the mechanism of a reasonably wide range of processes
of transfer of excitation energy (translational, rotational, vibrational, vibronic
(electronic-vibrational) of molecules and radicals, and electronic of atoms) in collisions of atoms, as well as diatomic and polyatomic species with each other and
atoms. Processes of translational and rotational excitations transfer have been
studied quite well by now. As we will see soon, they are very fast, and very often
we deal with local thermodynamic equilibrium for these degrees of freedom.
Therefore, we will pay the most attention to the processes of transfer of vibrational
and, especially, vibronic excitation energy.
5.1 Translational-Translational Energy Transfer
(T $ T Exchange)
We already touched on these processes when we discussed elastic atomic collisions.
From the course of mechanics, we know that even when material points or hard
balls collide, the kinetic energy of the motion of the particle as a whole or, in other
words, translational energy is exchanged. If a material point A having kinetic
energy E A collides with a fixed material point B then the first loses, and the second
acquires energy:
© Springer Nature Switzerland AG 2021
A. Pravilov, Gas-Phase Photoprocesses, Springer Series in Chemical Physics 123,
https://doi.org/10.1007/978-3-030-65570-9_5
153
Energy Transfer in Collisions
Abstract Inelastic collision processes, namely, processes of energy exchange of
translational motion (T-T exchange), a transformation of translational, and rotational energy (R-T exchange), a transformation of vibrational energy (V-T, V-R and
V-V exchange) are discussed briefly. Then perturbation-facilitated and
perturbation-irrelevant collision-induced non-adiabatic transitions (CINATs), and
other processes in which CINATs occur, are considered. CINATs between halogen
ion-pair states are examined in detail.
We are starting to discuss the mechanism of a reasonably wide range of processes
of transfer of excitation energy (translational, rotational, vibrational, vibronic
(electronic-vibrational) of molecules and radicals, and electronic of atoms) in collisions of atoms, as well as diatomic and polyatomic species with each other and
atoms. Processes of translational and rotational excitations transfer have been
studied quite well by now. As we will see soon, they are very fast, and very often
we deal with local thermodynamic equilibrium for these degrees of freedom.
Therefore, we will pay the most attention to the processes of transfer of vibrational
and, especially, vibronic excitation energy.
5.1 Translational-Translational Energy Transfer
(T $ T Exchange)
We already touched on these processes when we discussed elastic atomic collisions.
From the course of mechanics, we know that even when material points or hard
balls collide, the kinetic energy of the motion of the particle as a whole or, in other
words, translational energy is exchanged. If a material point A having kinetic
energy E A collides with a fixed material point B then the first loses, and the second
acquires energy:
© Springer Nature Switzerland AG 2021
A. Pravilov, Gas-Phase Photoprocesses, Springer Series in Chemical Physics 123,
https://doi.org/10.1007/978-3-030-65570-9_5
153