MOLECULAR-BEAM LASER SPECTROSCOPY OF SOME NEW BAND SYSTEMS OF THE NIOBIUM DIMER MOLECULE

Jet-cooled fluorescence excitation spectra of some new electronic band systems of the niobium dimer molecule are reported. The molecules wer e generated by pulsed laser vaporization of a niobium target rod and c ooled by supersonic expansion in helium. Rotationally resolved spectra of four new band systems in the region 653-686 nm were obtained using a single-mode ring dye laser to excite fluorescence. The Doppler-limi ted experimental resolution was 200 MHz. Of the four systems observed, all of which originate from electronically excited states, three are tentatively assigned as 1GAMMA(u) <-- 1GAMMA(g), 3PI0+/- <-- 3PI0+/-, and 3DELTA(u) <-- 3DELTA(g) transitions. Results are discussed in ligh t of theoretical predictions of the electronic structure of the Nb2 mo lecule. (C) 1994 Academic Press, Inc.