Differential cross sections for rotational excitation of NH3 by collisions with Ar and He: Close coupling results and comparison with experiment

Abstract

By means of the close coupling method we have calculated state-to-state differential and integral cross sections for rotational excitation and inversion of NH3 by collisions with Ar and He. For NH3–Ar we used an empirical and a scaled ab initio potential, for NH3–He an ab initio potential. The differential cross sections for NH3–Ar obtained from the empirical potential have an angular dependence that is in closer agreement with experiment than those obtained from the scaled ab initio potential. The integral cross sections are reproduced equally well by the two potentials. Also for NH3–He the differential cross sections are in accordance with experiment. For the integral cross sections the agreement is good too, except for the very small cross sections to some of the higher rotationally excited states. For both complexes the differential cross sections show a strong dependence on energy, both in their angular dependence and in their relative magnitudes.

State-to-state resolved differential cross sections for rotationally inelastic scattering of ND3with He

“…However, experimental also reported for this system, 18,19 alculations presented in Ref without selection of the inversion symmetry of the initial state associated with the umbrella vibrational mode. These collisions are complemented in the current study by detailed investigation of the scattering of molecules in collisions with He.…”

“…While work in the Nijmegen laboratory on cold collisions is presently ongoing, this paper describes collisions of ND 3 with He for higher energy where smooth trends in the DCSs and ICSs are expected. 75 Inelastic collisions of NH 3 with He 16,18,19 have been the subject of extensive previous study, with an emphasis on determination of ICSs and collision rates. However, experimental and theoretical DCSs were also reported for this system, although, with the exception of calculations presented in Ref [18], without selection of the inversion symmetry state associated with the umbrella vibrational mode.…”

“…75 Inelastic collisions of NH 3 with He 16,18,19 have been the subject of extensive previous study, with an emphasis on determination of ICSs and collision rates. However, experimental and theoretical DCSs were also reported for this system, although, with the exception of calculations presented in Ref [18], without selection of the inversion symmetry state associated with the umbrella vibrational mode. These 5 measurements of DCSs for NH 3 collisions are complemented in the current study by detailed investigation of the scattering of ND 3 molecules in collisions with He.…”

“…Although there is a ttering of diatomic molecules, such detailed experimental and computational investigations for scattering of polyatomic molecules remain A number of PESs have been developed previously for the scattering system. In addition, theoretical DCSs 29 using the coupled et al 18 The experimental measurements were performed in a crossed beam scattering machine located in the Nijmegen laboratory and shown schematically in Figure 1. Beams of ND 85 carrier gas) and the collider gas intersected at 90 vacuum chamber, and ND 3 molecules scattered into various rotational levels were detected with rotational level and inversion symmetry resolution using REMPI and VMI.…”

Scattering of NH3 and ND3 with rare gas atoms at low collision energy

“…4,5 On the other hand, the NH 3 -Ar complex has been the subject of numerous studies that focused either on its spectra [6][7][8][9] or on the collision dynamics through the measurement and analysis of integral and differential cross sections. [10][11][12][13][14][15] Although the literature is less extensive regarding the other NH 3 -Rg complexes, these systems have also been studied experimentally in spectroscopic [16][17][18][19] or molecular beam experiments. 20,21 Recent advances on the manipulation and control of molecular beams have renewed interest in these systems.…”