MULTIPHOTON STUDIES OF JET-COOLED XE-2 NEAR THE XE-ASTERISK-5D[5 2](0)(3) STATE - CHARACTERIZATION OF THE GROUND AND EXCITED-STATE POTENTIAL CURVES/

The two-photon resonant, three-photon (2+1) ionization spectra of jet- cooled (XeXe)-Xe-m-Xe-n, at energies near the Xe 5d[5/2](0)(3) state, are reported. A new progression has been observed and is attributed t o transitions from the van der Waals ground state, X(1) Sigma(g)(+)(0( g)(+)), through bound vibrational levels of an excited state of gerade symmetry. The analysis of some 26 closely spaced vibronic bands and i sotope effects provides information on the excited and ground state po tential energy curves. The vibrational quantum number of the lowest fr equency band near 82 539.1 cm(-1) is assigned to upsilon'=6+/-1. For u psilon'=6 this leads to molecular constants T'(e) congruent to 82 514. 9 cm(-1), omega'(e) congruent to 5.7955 cm(-1), and omega(e)x'(e) cong ruent to 0.07491 cm(-1). The upper state can be described by a morse p otential with dissociation energy D'(e) congruent to 112.10 +/- 0.05 c m(-1) and internuclear separation R'(e) congruent to 5.51 +/- 0.03 Ang strom. This is consistent with assignment to a rydberg molecular state of either the B (II1/2g)-I-2 or D (2) Sigma(1/2g)(+) ion core. At the Xe S-1(0)+Xe 5d[5/2](0)(3) threshold the molecular spectrum terminat es and continuum absorption is evidenced by a rise and fall in the fra gment ion yield. The direct determination of the dissociation limit fo r the excited state is used to derive the ground state dissociation en ergy D''(e) congruent to 196.32 +/- 0.05 cm(-1).