VIBRATIONAL STRUCTURE OF THE (2)(1)SIGMA(-X(1)(1)SIGMA(+)(G) TRANSITION OF THE BA-2 MOLECULE()(U))

Resonant two photon ionization (R2PI) technique was used to obtain the excitation spectrum of the Ba, molecule. A group of 12 vibrational ba nds was found in the 740-764 nm region. As a result of mass selective detection, they were attributed unambiguously to the Ba, molecule. By comparison to recent theoretical calculations, those bands were assign ed to the (2)(1)Sigma(u)(+)-X(1)(1)Sigma(g)(+) transition; they may be fitted to give the following vibrational constants (in cm(-1)): omega (e)('') = 33.2 +/- 0.2, omega(e)('')x(e)('') = 0.5 +/- 0.2, omega(e) = 65.2 +/- 0.2, and omega(e)(')x(e)(') = 0.4 +/- 0.2. (C) 1998 Academic Press.