OPTICAL-OPTICAL DOUBLE-RESONANCE AND FOURIER-TRANSFORM SPECTROSCOPY -THE RB-2 B-1-PI(U) ELECTRONIC-STATE UP TO THE QUASI-BOUND ENERGY-LEVELS

Nearly all quasibound vibrational energy levels of the Rb-2 B-1 Pi(u) state were accessed via a double resonance excitation scheme. A resona nt excitation process, X-1 Sigma(g)(+) --> A(1) Sigma(u)(+) --> (2)(1) Pi(g) has been used to populate single re-vibrational levels of the u pper (2)(1) Pi(g) state. Spectra of the (2)(1) Pi(g) --> B-1 Pi(u) inf rared fluorescence were recorded by high resolution Fourier transform spectroscopy. Taking account of previously studied B-1 Pi(u) --> X-1 S igma(g)(+)+ fluorescence spectra led to accurate effective molecular c onstants for the B-1 Pi(u) state. The line broadening due to the tunne ling effect was observed for the uppermost vibrational levels. The bar rier height was found to be approximate to 205 cm-l above its asymptot ic limit (5S(1/2) + 5P(3/2)) at 9.14 Angstrom. (C) 1997 Elsevier Scien ce B.V.