Jerosimić Stanka V, Gianturco Franco A, Wester Roland
Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, PAC 105305, 11158 Belgrade, Serbia.
Phys Chem Chem Phys. 2018 Feb 21;20(8):5490-5500. doi: 10.1039/c7cp05573k.
The direct dynamical paths leading to Associative Detachment (AD) in the gas-phase, and specifically in the low-temperature regions of the Dark Molecular Clouds (DMC) in the ISM, or in cold trap laboratory experiments, are investigated with quantum chemical methods by using a high-level multi-reference Configuration Interaction (CI) approach that employs single and double excitations plus Davidson perturbative correction [MRSDCI(Q)] and the d-aug-cc-pV5Z basis set. The potential energy curves for H + CN are constructed for different directions of the H partner approaching the CN anion within the framework of the Born-Oppenheimer approximation. The present calculations found that the AD energetics at low temperature becomes favorable only along a selected range of approaching directions, thus showing that there is a preferred path of forming HCN at low temperatures, while that of forming its HNC isomer is found to be energetically forbidden. Given the existence in the ISM of different HCN/HNC ratios in different environments, we discuss the implications of our findings for selective formation of either isomer in the low-temperature conditions of the molecular cloud cores.
