Vibrational and rotational energy transfer in collisions of vibrationally excited HF molecules with Ar atoms

Abstract

The Ar-HCl potential energy surface from a global map-facilitated inversion of state-to-state rotationally resolved differential scattering cross sections and rovibrational spectral data This work presents converged vibrational close coupling-rotational coupled states calculations of cross sections and rate constants for rotational and vibrational transitions in collisions of vibrationally excited HF molecules with Ar atoms. Reduced channel basis sets assuming both a lower and an upper cutoff in vibrational quantum number are used for calculations at high internal energies of the diatomic molecule. The most recent potential energy surface is employed for the calculations and the correspondence of the results to the previous investigation of rovibrational dynamics in collisions of HF(vϭ1) with Ar is examined. It is shown that initial vibrational excitation stimulates vibrationally inelastic transitions to a great extent while the rotational energy transfer is essentially unaffected by initial v-number. The cross sections for vibrational relaxation of different vibrational levels of HF are shown to exhibit a strong dependence on initial rotational energy which is, however, of different magnitude for different vibrational states. The dependence of the vibrational relaxation of HF(vϭ1,3,6) on the translational energy of the atomic collision partner is different by an energy independent factor for different vibrational levels in the high energy limit and shows minima at low collision energies.

Projection-reduced close coupling calculations of cross sections for vibrational relaxation in collisions of diatomic molecules with atoms

“…This is so despite the fact that the cross section for total vibrational relaxation of HF(vϭ1, jϭ0) in collisions with Ar is predominantly determined by the cross sections for the ͉vϭ1, jϭ0͘→͉vϭ0, jϭ13͘ and ͉vϭ1, jϭ0͘ →͉vϭ0, jϭ14͘ transitions. 7,13,9 The cross sections for VR of HF(vϭ1, jϭ2) are well converged with ⍀ max ϭ2, the cross sections for VR of HF(vϭ1, jϭ3) are converged to within 1% when ⍀ max ϭ3 and the calculations with ⍀ max ϭ4 give essentially the same results for VR of HF(vϭ1, j ϭ4) as the full CC calculations. The difficulty of numerically solving Eq.…”

“…11,12 The calculations are performed on two most recent and accurate potentials and in order to make this comparison more meaningful it is necessary to delineate the validity of the CS approximation for vibrationally inelastic HFϩAr collisions. In our previous work 13 we have computed rate constants for one-quantum rotational transitions in ArϩHF collisions using the CS approach and the CC method. The observed deviation of the CS results from the CC rate constants reached 40% and it is interesting to see if the performance of the a͒ Current address: Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138.…”

Quantum dynamics of vibration–vibration energy transfer for vibrationally excited HF colliding with H2

“…For vibrationally excited species, choosing the full basis set is usually beyond the computational afford, so that a reduced channel dynamical approach should be employed in the calculations. In 2001, Krems and Nordholm introduced the vibrational‐state‐reduced basis set in the time‐independent dynamics calculations for the Ar–HF inelastic collisional system, in which only several neighboring vibrational states were selected in the basis set for a given HF initial vibrational state. dos Santos et al compared the cross‐sections for the quasi‐resonant transition H 2 ( v 1 = 1, j 1 = 0) + H 2 ( v 2 = 0, j 2 = 1) → H 2 () + H 2 () by applying the full basis set and an extremely reduced basis set with only four channels in the calculations.…”

“…(9) indicates that only selected CVSs are included in the basis set. Because of the large energy gaps between vibrational states in H 2 and HF molecules, a single vibrational quantum number transition is much more efficient than multiple vibrational quantum number transitions . Therefore, for a given initial vibrational state of H 2 or HF, only the eigenfunctions corresponding to the nearest neighbor vibrational states are included in the basis set.…”

Resonance and reversibility of vibrational relaxation of HF in high temperature Ar bath gas

“…Recently, we reported quantum calculations of rate constants for VR in HFϩAr collisions at low temperatures [30][31][32] with an accurate potential energy surface ͑PES͒ for the HF ϩAr interaction. [33][34][35] It was demonstrated that VR in HF(v ϭ1,jϭ0) has a near-resonant character and the rate constants for VR of HF(vϭ1,j) at room temperature increase significantly with the initial rotational quantum number j.…”