PHOTOIONIZATION SPECTROSCOPY OF GA-RARE GAS COMPLEXES

New electronic states, F 2 Delta(3/2), G (2) Delta(5/2), H (2) Pi(1/2) and I (2) Pi(3/2), are investigated for the complexes GaAr, GaKr, and GaXe with resonant two-photon photoionization spectroscopy. These exc ited states correlate to the D-2<--P-2 (4d<--4p) atomic transition of gallium. Vibronic structure in these spectra are used to obtain vibrat ional constants, and extrapolated progressions are used to determine d issociation energies. The upper (2) Delta states are more than twice a s strongly bound as the corresponding (2) Pi states. Excited state val ues of dissociation energies are used in energetic cycles to determine ground-state dissociation energies for GaAr, GaKr, and GaXe. In all t hree cases, the values obtained are significantly lower than previous estimates. The ground state of GaAr is extremely weakly bound, with D- 0 '' = 20+/-20 cm(-1), while the corresponding value for GaKr is only 35+/-20 cm(-1). The B (2) Sigma(+) excited states of the Ga-RG complex es are confirmed to have substantial barriers in their long-range pote ntials. (C) 1998 American Institute of Physics.