Phosphine interacting with argon: potential energy surface and line widths of PH3 perturbed by Ar

Abstract

The phosphine–Ar (PH₃–Ar) van der Waals complex's three-dimensional potential energy surface (3D-PES) was mapped along the intermonomer coordinates using the explicitly correlated Coupled Clusters approach. An analytical expansion of this 3D-PES is deduced. The complex characteristics of the intermolecular interactions between PH₃ and Ar, which are at the origin of the pressure broadening of the PH₃ rovibrational lines, are accurately described by this 3D-PES. Afterwards, the broadening of the phosphine lines perturbed by Ar at room temperature is computed using this 3D-PES. To be able to incorporate this 3D-PES into our collisional broadening computation software, we first modified it with a new “fractional” function. Then, we used the semiclassical Modified Robert and Bonamy model improved by the so-called notion of exact trajectory. For various branches of the ν₂ and ν₄ PH₃ rovibrational bands, room temperature data are provided. Our data agree with the experimental measurements. The precise estimation of PH₃ and Ar abundances in planetary atmosphere spectra should benefit greatly from the data provided here.