Collisional excitation of interstellar PN by H₂: new interaction potential and scattering calculations

Rotational excitation of interstellar PN molecules induced by collisions with H₂ is investigated. We present the first ab initio four-dimensional potential energy surface (PES) for the PN–H₂ van der Waals system. The PES was obtained using an explicitly-correlated coupled cluster approach with single, double, and perturbative triple excitations [CCSD(T)-F12b]. The method of interpolating moving least squares was used to construct an analytical PES from these data. The equilibrium structure of the complex was found to be linear, with the H₂ aligned at the N end of the PN molecule, at an intermolecular separation of 4.2 Å. The corresponding well-depth is 224:3 cm⁻¹. The dissociation energies were found to be 40.19 cm⁻¹ and 75.05 cm⁻¹ for complexes of PN with ortho-H₂ and para-H₂, respectively.
Integral cross-sections for rotational excitation in PN–H₂ collisions were calculated using the new PES, and were found to be strongly dependent on the rotational level of the H₂ molecule. These new collisional data will be crucial to improve the estimation of PN abundance in the interstellar medium from observational spectra.

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Desrousseaux, B., Quintas-Sánchez, E., Dawes, R., Marinakis, S. and Lique, F. 2021. Collisional excitation of interstellar PN by H₂: new interaction potential and scattering calculations. Journal of Chemical Physics. 154 (Art. 034304) and may be found at https://doi.org/10.1063/5.0039145.