Gas-phase infrared spectroscopy on the lowest triplet state of the pyrazine-argon complex

The infrared (IR) absorption spectrum of the jet-cooled pyrazine-argon Van der Waals complex in its lowest triplet state is measured. Vibrational exci tation of the laser-prepared triplet state by IR absorption causes dissocia tion of the complex, which is monitored via the depletion of the pyrazine-a rgon ion signal. A total of 10 vibrational transitions are detected in the 500-1500 cm(-1) region. Comparison of these data with ab initio calculation s might help to elucidate the nature of the distortion of the lowest triple t state by other electronically excited states. (C) 2000 Elsevier Science B .V. All rights reserved.