Full State-Resolved Energy Gain Profiles of CO2 (J = 2−80) from Collisions of Highly Vibrationally Excited Molecules. 1. Relaxation of Pyrazine (E = 37900 cm−1)

Efficient method is proposed for computing thermal rate constant of recombination reaction that proceeds according to the energy transfer mechanism, when an energized molecule is formed from reactants first, and is stabilized later by collision with quencher. The mixed quantum-classical theory for the collisional energy transfer and the ro-vibrational energy flow [M. Ivanov and D. Babikov, J. Chem. Phys. 134, 144107 (2011)] is employed to treat the dynamics of molecule + quencher collision. Efficiency is achieved by sampling simultaneously (i) the thermal collision energy, (ii) the impact parameter, and (iii) the incident direction of quencher, as well as (iv) the rotational state of energized molecule. This approach is applied to calculate third-order rate constant of the recombination reaction that forms the (16)O(18)O(16)O isotopomer of ozone. Comparison of the predicted rate vs. experimental result is presented.

Section: Discussionmentioning

confidence: 99%

Efficient quantum-classical method for computing thermal rate constant of recombination: Application to ozone formation

Ivanov

Babikov

2012

“…On the other side, we can work with the fluid rotor equations and substitute (13 ), (20), and (21) into (14 ). This leads to the matrix equation given in Appendix A.…”

Section: B Equivalence Of the Two Methodsmentioning

confidence: 99%

“…In recent years, the interest in collisional energy transfer at ultra-cold conditions has been high [14][15][16] and in those cases the inelastic scattering calculations must be done using the full-fledged quantum mechanics. 17,18 On the other hand, for the processes relevant to combustion, 19,20 photochemistry, 21,22 or hyper-thermal phenomena, 23,24 when high energies are involved, the classical-trajectory picture is quite appropriate. [25][26][27][28][29] In between those limits, the quantum mechanical calculations of collisional energy transfer become unaffordable computationally even for the smallest molecular systems (due to a large number of coupled channels and partial waves) while the classical trajectory calculations are not entirely justified and contain serious drawbacks (such as a) Author to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Equivalence of the Ehrenfest theorem and the fluid-rotor model for mixed quantum/classical theory of collisional energy transfer

Семенов

Babikov

2013

The theory of two seemingly different quantum/classical approaches to collisional energy transfer and ro-vibrational energy flow is reviewed: a heuristic fluid-rotor method, introduced earlier to treat recombination reactions [M. Ivanov and D. Babikov, J. Chem. Phys. 134, 144107 (2011)], and a more rigorous method based on the Ehrenfest theorem. It is shown analytically that for the case of a diatomic molecule + quencher these two methods are entirely equivalent. Notably, they both make use of the average moment of inertia computed as inverse of average of inverse of the distributed moment of inertia. Despite this equivalence, each of the two formulations has its own advantages, and is interesting on its own. Numerical results presented here illustrate energy and momentum conservation in the mixed quantum/classical approach and open opportunities for computationally affordable treatment of collisional energy transfer. © 2013 AIP Publishing LLC.

“…There have been numerous studies on CET between highly vibrationally excited polyatomic molecules and various bath gases. Previous studies include highly vibrationally excited benzene, [1][2][3] deuterated and halogenated benzenes, 1,[3][4][5][6][7] alkyl benzenes, 8 azulene, 9 naphthalene, 10 cycloheptatrienes, 11 and pyrazine 12 in a range of atomic and molecular baths including noble gases, 1 CO 2 , [3][4][5]12,13 N 2 , 6,7 and H 2 O. 14 The photophysics of highly vibrationally excited benzene has been the subject of numerous studies.…”

Section: Introductionmentioning

confidence: 99%

Resolving the energy and temperature dependence of C6H6∗ collisional relaxation via time-dependent bath temperature measurements

West

Winner

Bowersox

et al. 2016

The relaxation of highly vibrationally excited benzene, generated by 193 nm laser excitation, was studied using the transient rotational-translational temperature rise of the N2 bath, which was measured by proxy using two-line laser induced fluorescence of seeded NO. The resulting experimentally measured time-dependent N2 temperature rises were modeled with MultiWell based simulations of Collisional Energy Transfer (CET) from benzene vibration to N2 rotation-translation. We find that the average energy transferred in benzene deactivating collisions depends linearly on the internal energy of the excited benzene molecules and depends approximately linearly on the N2 bath temperature between 300 K and 600 K. The results are consistent with experimental studies and classical trajectory calculations of CET in similar systems.