Laser optogalvanic study of HCO A state predissociation

Widths of lines in the (0, 90, 0)–(0, 01, 0) band of the HCO ? 2A\–? 2A′ transition are recorded using a single-mode dye laser, revealing a strong dependence on the rotational quantum number N. The HCO radical is produced in a radio frequency discharge in acetaldehyde (CH3CHO) vapor and the ?–? transition in the 570–630 nm region is detected by laser-induced changes in the discharge impedance. The variation of widths with N is interpreted in terms of Coriolis interaction and K-type resonance of the (0, 90, 0)Σ(K′ = 0) level with nearby strongly predissociated Π(K′ = 1) and Δ(K′ = 2) levels, respectively, of the upper state.