Resonance-enhanced multiphoton ionisation spectroscopy of jet-cooled bis(η6-benzene)chromium

The molecules of bis(eta(6)-benzene)chromium cooled in a supersonic jet are ionised efficiently by nanosecond pulses of a tuneable dye laser operating in the region of the 3d(2) --> R4p(x,y) Rydberg transition (26 600-27 100 cm(-1)). The mass spectra reveal a surprisingly strong signal from the intact molecular ions. The yield of the molecular ions increases in a two-colour experiment. The resonance-enhanced multiphoton ionisation (REMPI) spectra reveal two vibronic components of the Rydberg transition at 26 754 and 27 017 cm(-1). The distance between these peaks (263 cm(-1)) corresponds to the frequency of the symmetric metal-benzene stretch in the Rydberg state. (C) 2003 Elsevier Science B.V. All rights reserved.