Full-dimensional quantum wave packet study of rotationally inelastic transitions in H2+H2 collision

Abstract

We report full-dimensional accurate quantum dynamical calculations of the rotationally inelastic collision: para-H 2 ( 1 ϭ0,j 1 ϭ0)ϩpara-H 2 ( 2 ϭ0,j 2 ϭ0)→para-H 2 ( 1 ϭ0,j 1 Ј)ϩpara-H 2 ( 2 ϭ0,j 2 Ј), using a wave packet approach based on the Chebyshev polynomial expansion of Green's operator. The six-dimensional Hamiltonian within the coupled-states approximation is discretized in a mixed grid/basis representation and its action is computed in appropriate representations facilitated by a series of one-dimensional pseudo-spectral transformations. Both the parity and diatomic exchange symmetry are adapted. The S-matrix elements for the rotational transitions are obtained at all energies by the Fourier transform of Chebyshev correlation functions and used to compute transition probabilities, differential and integral cross sections, and state-resolved thermal rate constants. Results are compared for two recently proposed ab initio based potential energy surfaces and with previous quantum results.

Fully converged integral cross sections of collision induced dissociation, four-center, and single exchange reactions, and accuracy of the centrifugal sudden approximation in H2 + D2 reaction

“…Another area of interest in the study of the H 4 system are the calculation of nonreactive vibrational de-excitation cross sections using full-dimensional QM methods of both time-independent [46][47][48][49] and time-dependent type. 50,51 Recently, we performed full-dimensional time-dependent wave packet calculations of the H 2 + D 2 reaction and its isotopic variants on the ASP and BMKP PESs with J = 0. 52 The role of both vibrationally and rotationally excited reagents was examined.…”

Vibration-vibration and vibration-translation energy transfer in H2-H2 collisions: A critical test of experiment with full-dimensional quantum dynamics

“…13,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] Quantum calculations are the primary source of state-resolved rate coefficients for astrophysical modeling. Excitation of rotational and vibrational levels of H 2 by collisions with H, H + , He, H 2 , and electrons followed by emission of quadrupole radiation is considered to be the main cooling mechanism of the primordial gas.…”

“…As a result, many of the early H 2 -H 2 calculations resorted to the rigid-rotor approximation. However, in the last several years, a number of full-dimensional quantum calculations have been reported within the timedependent 45,47,[49][50][51][52] and time-independent 13, 44, 46, 53-55 quantum formalisms. Some of these calculations have adopted the coupled-states approximation, [44][45][46][47] which was shown to be reliable.…”

“…However, in the last several years, a number of full-dimensional quantum calculations have been reported within the timedependent 45,47,[49][50][51][52] and time-independent 13, 44, 46, 53-55 quantum formalisms. Some of these calculations have adopted the coupled-states approximation, [44][45][46][47] which was shown to be reliable. Recent calculations from our group have adopted the full close coupling method within the time-independent quantum formalism 13, 53-55 and largely explored interesting features of molecule-molecule collisions at temperatures in the cold and ultracold regimes, where quantum effects play a dominant role.…”

A comparative study of the low energy HD+o-/p-H2 rotational excitation/de-excitation collisions and elastic scattering

“…These PESs have been used in several different calculations. [32][33][34][35][36] However, in our previous works 12,34 we found that in the case of low energy H 2 +H 2 collision these PESs provide different results for some specific state-resolved cross sections. The difference may be up to an order of magnitude.…”