Photodissociation spectroscopy of CaCH4+

Abstract

We report on studies of the structure and dissociation of CaCH4+ and its isotopomer CaCD4+, using photodissociation spectroscopy. Molecular absorption bands are observed to the red of the Ca+ (4p 2P←4s 2S) resonance transition. The photodissociation action spectrum shows evidence for spin–orbit doubling and complex rovibrational structure. No reactive quenching product is observed. The transition is assigned as 2E←2A1 in C3v geometry. The spin–orbit constant in the upper state is found to be Aso=111±4 cm−1. The action spectrum shows a strong progression in the Ca+–CH4 (CD4) intermolecular stretch in the 2E state with a fundamental stretch frequency of ωs′=270±16(244±4) cm−1. Weaker intermolecular bending vibration is also apparent, with a fundamental bending frequency of ωb′=112±16(92±14) cm−1 for Ca+–CH4(CD4). The resonances show evidence for predissociation broadening. These results differ markedly from our previous results on the analogous MgCH4+ system.