òΣ⁺ → [Xtilde]²Π_i emission spectra of the supersonically cooled cations HCP⁺ and DCP⁺

Abstract

The emission spectra of the à ²Σ⁺ → [Xtilde] ²Π _i electronic transition of rotationally cooled HCP⁺ and DCP⁺ cations have been obtained using electron impact excitation of seeded helium supersonic free jets. The resulting narrowing of the rotational envelopes enables weak transitions associated with single and double excitation of the degenerate v ₂ bending mode in the [Xtilde] ²Π _i state to be identified. The profiles of the bands are also used as a diagnostic tool in the assignments. The vibronic structure in the spectra, which is complicated by Renner and Fermi effects, has been analysed in terms of the parameters characterizing these interactions.