Photodissociation spectroscopy of Ca+-rare gas complexes

Weakly bound complexes of the form Ca+-RC (RG = Ar, Kr, Xe) are prepared in a pulsed nozzle/laser vaporization cluster source and studied with mass-selected resonance enhanced photodissociation spectroscopy. The Ca+ (P-2<--S-2) atomic resonance line is the chromophore giving rise to the molecular spectra in these complexes. Vibrationally resolved spectra are measured for these complexes in the corresponding 2 Pi<--X(2) Sigma(+) , molecular electronic transition. These spectra are red shifted from the atomic resonance line, indicating that each complex is more strongly bound in its excited (2) Pi state than it is in the ground state. Vibronic progressions allow determination of the excited state vibrational constants: Ca+-Ar, omega'(e) 165 cm(-1); Ca+-Kr, omega'(e) = 149 cm(-1); Ca+-Xe, omega'(e) = 142 cm(-1). Extrapolation of thr: excited state vibrational progressions, acid combination with the known atomic asymptotes and spectral shifts, leads to determination of the ground state dissociation energies Ca+-Ar, D ''(0) = 700 +/- 100 cm(-1) (0.09 eV); Ca+-Kr, D ''(0) = 1400 +/- 150 cm(-1) (0.17 eV); Ca+-Xe, D ''(0) = 2300 +/- 150 cm(-1) (0.29 eV). The spin-orbit splitting in the (2) Pi(1/2,3/2) state for these complexes is larger than expected by comparison to the Ca+ atomic value. (C) 1996 American Institute of Physics.