Spectroscopy of the 3p 2Π Rydberg state of HCO by resonance-enhanced multiphoton ionization

High resolution two-photon resonant, three-photon ionization spectra of HCO and DCO are presented for wavelengths from 373 to 460 nm. Rotational analysis of the (K′,K″)=(0,2) and (0,1) subbands and measurements of spin–rotation splitting on the (0,2) subband provide a definitive assignment of the (070)←(000) band of the bent-to-linear 3p 2Π(A″)←X̃ 2Π(A′) Rydberg absorption in HCO. Bands from nine vibrational states in HCO and ten in DCO, attributable to a (0n0)←(000) bending mode progression in the 3p Rydberg state, are observed and assigned. Additional bands in HCO and DCO are assignable to (0n1)←(000) 3p progressions. Values for the 3p 2Π fundamentals ν2=822.1(0.7) cm−1, ν3=2177(3) cm−1 for HCO and ν2=657(2) cm−1, ν3=1900(5) cm−1 for DCO were measured. Additional unassigned partial progressions are provisionally attributed to 3s 2∑+←X̃ 2Π(A′) transitions.