CCSD(T) Determination of the Vibrational Structure in the Ã2Σ+ ← X̃2Π Spectrum of CCO-

Abstract

An ab-inito quartic force field of CCO− in its first excited state Ã2∑+ is calculated from an aug-cc-VTZ basis set at CCSD(T) level of theory in order to compute the vibrational energy levels in the range 600−4800 cm-1. A variational-perturbational approach is used to diagonalize the most important vibrational configurations constructed from harmonic vibrational wave functions. The result agree well with the most reliable experimental values studied in a neon matrix and predict as yet unobserved overtones bands in the vibrational structure of the Ã2∑+ ← X̃2Π spectrum of CCO-.