Vibronic structure of the 2 Π u ground electronic state of dicyanoacetylene cation revisited by PFI-ZEKE photoelectron spectroscopy and ab initio calculations
Résumé
(2015): Vibronic structure of the 2 Π u ground electronic state of dicyanoacetylene cation revisited by PFI-ZEKE photoelectron spectroscopy and ab initio calculations, Molecular Physics, The X +2 u ← X 1 + g transition of dicyanoacetylene has been recorded for the first time using pulsed-field-ionisation zero-kinetic-energy photoelectron spectroscopy. The analysis of the photoelectron spectrum allowed an accurate determination of the adiabatic ionisation potential of C 4 N 2 (E i, ad. /hc = 95,479 ± 2 cm −1) and a description of the vibrational structure of the electronic ground state of the cation which is affected by the Renner–Teller effect and the spin–orbit interaction. The spin–orbit coupling constant was measured as −52 ± 2 cm −1. These results are supported by ab initio calculations performed at the complete active space self-consistent field and second-order perturbation theory levels of theory, with extrapolation to the complete basis set limit.