15min:

MICHAEL P. ZIEMKIEWICZ, CHRISTIAN PLUETZER AND DAVID J. NESBITT, JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado, USA; YOHANN SCRIBANO, CNRS-Universit´e de Bourgogne, Dijon, France; ALEXANDRE FAURE, CNRS, Institut de Plan´etologie et d’Astrophysique de Grenoble(IPAG), France; AND AD VAN DER AVOIRD, Radboud University, Nijmegen, The Netherlands.

We present spectroscopic studies on the H₂-H₂O complex, providing information on the binding of these astrochemically-significant molecules. Understanding this interaction is crucial for further understanding the production of H₂ from atomic hydrogen on interstellar dust grain surfaces, which are often covered with an icy mantel. We generate these clusters using a slit supersonic jet expansion which cools to below 5 K, a temperature which is sufficiently low for observing this species whose binding energy is ~ 60 cm^-1. The experimental detection method consists of an infrared vibrational excitation followed by a 193 nm pulse to photolyze H₂O and laser induced fluorescence on the OH product. In conjunction with theoretical studies presented in the accompanying talk, we identify two overtone bands associated with excitation of the |02-\rangle |00+\rangle transition in the water moiety. Theory and experiment agree to within 0.2 cm^-1, which attests to the accuracy of the method used to make predictions, as shown in the accompanying talk. Additional time and frequency domain measurements are performed with this three laser experiment to obtain information on predissociation dynamics, where internal H₂O vibration is transferred to the intermolecular coordinate. Theoretically-generated excited state wavefunctions are used to obtain further insight into the significant dependence of predissociation lifetime on the upper state in the infrared cluster transition.