Induced rotational excitation of the fluoromethylidynium ¹²CF⁺ and ¹³CF⁺ through collision with helium

¹ Laboratoire de Spectroscopie Atomique Moléculaire et Applications, Faculté des Sciences, Université Tunis el Manar, 2092 Tunis, Tunisie
e-mail: yosra-aji@hotmail.fr
² Université Paris-Est, Laboratoire Modélisation et Simulation Multi-Échelle, MSME UMR 8208 CNRS, 5 Bd Descartes, 77454 Marne-La-Vallée, France

Received: 14 December 2012
Accepted: 11 June 2013

Abstract

Aims. The present paper focuses on the calculation of the collision rate coefficients for rotational excitation of the ¹²CF⁺ and its isotopologue ¹³CF⁺ by He for temperature ranging from 10 to 300 K.

Methods. A two-dimentional (2D) potential energy surface (PES) of the CF⁺(X¹Σ⁺)-He(¹S) system is calculated at the ab initio coupled cluster with single, double, and perturbative triple excitation level of theory with the aug-cc-pV5Z basis set. The basis set superposition errors were taken into account in our computation. Dynamical calculations of state-to-state rotational integral cross sections of the CF⁺ by collision with He were performed using the close-coupling method.

Results. The PES presents a global minimum of ~212 cm^-1 below the CF⁺-He dissociation limit. Collisional cross sections among the first 11 rotational levels of CF⁺ were calculated for total energies up to 1500 cm^-1. Downward rate coefficients between the rotational levels were calculated for temperature ranging from 10 to 300 K. A propensity toward an even parity of ΔJ is observed.