Formaldehyde: Electronic structure calculations for the S and T1 states

Many-body perturbation theory (MBPT) and coupled-cluster method calculations are reported for the S0(X 1A1) and T1(a 3A″) electronic states of formaldehyde. The structural parameters for the S0 minimum (RCH = 1.102 Å, RCO = 1.211 Å, HCH = 116.2°) and the T1 minimum (RCH = 1.085 Å, RCO = 1.327 Å, HCH = 118°, ’’out-of-plane’’ angle = 37° 12′) agree well with experimentally deduced values. Calculated heats of reaction for dissociation to radical products and molecular products agree well with literature values. The energy barriers for dissociation to molecular products and rearrangement to hydroxycarbene are presented. Vertical and adiabatic transition energies are reported for S0→T1, while a vertical transition energy for S0→S1 is reported.