Electronic Structure and Rydberg-Core Interactions in Hydroxycarbene and Methylhydroxycarbene.

Vertical and adiabatic excitation energies and oscillator strengths for valence and Rydberg states of hydroxycarbene (HCOH) and methylhydroxycarbene (CH3COH) are reported. The electronic properties were computed with equation-of-motion coupled-cluster methods with single and double substitution methods (EOM-CCSD) and the aug-cc-pVTZ basis set. The states' characters were analyzed by plotting natural transition orbitals (NTOs). The calculations demonstrate that the shape, size, and energy of each Rydberg orbital are affected to varying degrees by their interaction with the ion core. Likewise, the corresponding quantum defects reflect the Rydberg electron-ion core interactions. The results reported herein, combined with previously reported calculations of the photoelectron spectrum of HCOH, should help in designing strategies for state-selective detection of hydroxycarbenes via ionization.