High level ab initio studies on the excited states of HOCO radical

Abstract

The HOCO radical has a ground (X 2A′) and two lowest A″2 excited states that are located using the CCSD(T) level of theory with the cc-pVDZ and cc-pVTZ basis sets. The harmonic frequencies are calculated at the CCSD(T) level of theory with the cc-pVDZ basis set. The vertical excitation energies for the 2 2A′, 3 2A′, 1 2A″, and 2 2A″ states of HOCO are obtained at the MRCI level of theory with the cc-pVTZ and aug-cc-pVTZ basis sets. The first excited state (1 2A″) is calculated to be 70.7 kcal mol−1 above the ground state for trans-HOCO. Comparisons are made between the excited states of HOCO and HCO. It is demonstrated that the HOCO states are not similar to those of HCO.