Laser fluorescence excitation spectroscopy of the GeAr van der Waals complex

Laser fluorescence excitation spectra of the GeAr van der Waals complex, in the vicinity of the individual fine-structure lines of the Ge 4s(2)4p5s (3)Pdegrees<--4s(2)4p(2 3)P atomic resonance transition in the region 275-260 nm are reported. Excited-state (v',0) progressions of bands built upon the individual J'<--J" fine-structure atomic lines were observed. In all cases, the progressions terminated with a broad, unstructured band characteristic of the existence of a barrier in the excited-state potential energy curves. Assignment of the v' vibrational quantum numbers for the resolved bands was successfully carried out through analysis of the (GeAr)-Ge-70,72,74,76 isotope splittings of the bands. Rotational analyses of the resolved bands were carried out, and upper- and lower-state Omega assignments and determination of the rotational constants could be performed. Transitions out of lower Omega'=0(+), 1, and 0(+) levels associated with the asymptotic Ge(4s(2)4p(2 3)P) J'=0, 1, and 2 atomic fine-structure levels, respectively, were observed. To derive information on the relevant Ge+Ar interactions, the observed spectra were interpreted through model potential energy curves based on the isoelectronic SiAr system. The large spin-orbit interaction of the Ge atom has a strong effect on the nonbonding interactions of the fine-structure levels with the Ar atom. (C) 2003 American Institute of Physics.