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 excitation of the laser-prepared triplet state by IR absorption causes dissociation of the complex, which is monitored via the depletion of the pyrazine-argon ion signal. A total of 10 vibrational transitions are detected in the 500-1500 cm(-1) region. Comparison of these data with ab initio calculations might help to elucidate the nature of the distortion of the lowest triplet state by other electronically excited states. (C) 2000 Elsevier Science B.V. All rights reserved.