Full-dimensional quantum dynamics of CO in collision with H2

Abstract

We report the first full-dimensional potential energy surface (PES) and quantum mechanical close-coupling calculations for scattering of SiO due to H 2. The full-dimensional interaction potential surface was computed using the explicitly correlated coupled-cluster (CCSD(T)-F12b) method and fitted using an invariant polynomial approach. Pure rotational quenching cross sections from initial states v 1 = 0, j 1 =1-5 of SiO in collision with H 2 are calculated for collision energies between 1.0 and 5000 cm −1. State-to-state rotational rate coefficients are calculated at temperatures between 5 and 1000 K. The rotational rate coefficients of SiO with para-H 2 are compared with previous approximate results which were obtained using SiO-He PESs or scaled from SiO-He rate coefficients. Rovibrational state-to-state and total quenching cross sections and rate coefficients for initially excited SiO(v 1 = 1, j 1 =0 and 1) in collisions with para-H 2 (v 2 = 0, j 2 = 0) and ortho-H 2 (v 2 = 0, j 2 = 1) were also obtained. The application of the current collisional rate coefficients to astrophysics is briefly discussed.

All-dimensional H2–CO potential: Validation with fully quantum second virial coefficients

“…19,20 We found this to be impossible for two reasons. The first problem is with the long-range behavior of that potential, which fails to decay to zero at long range if the intramolecular distances r and s differ from their equilibrium values.…”

“…19,20 PES using the (original) intermonomer potential subroutine from the Supporting Information of Ref. 20 and adding to it the same intramonomer potentials as used in U tot,15 .…”

“…Yang and coworkers 19,20 recently developed a 6D potential for H 2 -CO and used it in scattering calculations. The cross-sections were generally in qualitative agreement with experiment for low-energy scattering, but this agreement was not as good as that for cross-sections calculated from the 4D potential of Refs.…”

Perspective: Ultracold molecules and the dawn of cold controlled chemistry

“…The relaxation pathway was found to be mostly dominated by ∆ j = −1 transitions, for temperatures in the 1-1000 K range. In a more recent work, Yang et al 168,169 reported the first full-dimensional computation of rovibrational transitions in CO by H 2 at temperatures ranging from 1-100 K. Complex scattering lengths for collisions of linear and non-linear polyatomic molecules, CO 2 , H 2 O and NH 3 , with He have recently been reported by Yang and co-workers. 170 The ratio of the imaginary to real components of the scattering length, β/α, was found to generally increase with decreasing rotational constant.…”

Inelastic cross sections and rate coefficients for collisions between CO and H2

“…and compared against 6D-CC results obtained perviously 15 . Figure 2 shows elastic and rotationally inelastic cross sections for the (1, 1, 0, 0) initial state.…”