Photodissociation spectroscopy of CaCH4+

We report on studies of the structure and dissociation of CaCH4+ and its isotopomer CaCD4+, using photodissociation spectroscopy. Molecular absorption bands an observed to the red of the Ca+ (4p P-2 <-- 4s S-2) resonance transition. The photodissociation action spectrum shows evidence for spin-orbit doubling and complex rovibrational structure. No Inactive quenching product is observed. The transition is assigned as (2)E <-- (2)A(1) in C-3 upsilon geometry. The spin-orbit constant in the upper state is found to be A(SO) = 111 +/- 4 cm(-1). The action spectrum shows a strong progression in the Ca+-CH4 (CD4) intermolecular stretch in the (2)E state with a fundamental stretch frequency of omega(s)' = 270 +/- 16(244 +/- 4) cm(-1). Weaker intermolecular bending vibration is also apparent, with a fundamental bending frequency of omega(b)' = 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. (C) 1997 American Institute of Physics.