Ab initio predictions of the spectroscopic parameters of the germanium halomethylidyne (Ge=C-X; X=F, Cl, Br) free radicals

Abstract

Ab initio methods have been used to predict the spectroscopic parameters for the X ˜ 2 Π i and A ˜ 2 Σ + states of the unknown germanium halomethylidyne (GeCX, X=F, Cl, Br) free radicals. The predictive powers of the chosen ab initio methods have been tested on the known GeCH radical. The calculations show the linear Ge CX (X=F, Cl, Br) isomer is the global minimum on the potential energy surface, with the cyclic XGeC isomer being between 6400 (BrGeC) and 11300 (FGeC) cm −1 higher in energy. The ground state geometries, vibrational frequencies, spin-orbit coupling and Renner parameters have been calculated using the cc-pVTZ basis set. The excited state geometries, vibrational frequencies and excitation energies have also been calculated, and the rotational contours of the 0 0 0 bands have been simulated at medium resolution under jet-cooled conditions. These calculations will aid in the search of these unknown radicals.