The Hgndash;NH3complex has been studied by forming the complex in a supersonic jet and probing the boundhyphen;tohyphen;bound transitions to the two excited electronic states correlated to Hg(6thinsp;3P1)+NH3. Laserhyphen;induced fluorescence and action spectroscopy have been combined with isotopic studies to map out the characteristics of these states. Both excited states are found to be bound by more than 5000 cmminus;1, over 20 times greater than the ground state binding energy. Extensive vibrational structure is found and interpreted in terms of a stretching progression of the Hgndash;NH3bond and bending of the NH3moiety with respect to the mercury atom. The two states show striking differences in their behavior with respect to predissociation to Hg(6thinsp;3P0). TheBtilde; state is not observed in fluorescence, but predissociates efficiently to Hg(3P0)+NH3, while theAtilde; state shows predominant fluorescence with only a minor amount of Hg(6thinsp;3P0) formation. Rotational band contour analysis has been used to assign theBtilde; state as the3Eand theAtilde; state as the3A1state. Both states are characterized by a shortening in the Hgndash;N bond distance from 3.35 Aring; in the ground state to about 2.2 Aring; in either excited state. The rotational contour assignments show that the electronic angular momentum of the excited mercury atom is preserved in the complex despite the complexrsquo;s polyatomic nature. This allows an interpretation of the electronic relaxation in a quasidiatomic fashion. All our results are consistent with aC3vgeometry for the Hgndash;NH3complex in both the ground and excited states. The characteristics of theAtilde; andBtilde; states and their couplings to theatilde; state correlated to3P0enable a comparison with the fullhyphen;collision studies and has led us to postulate theAtilde; andBtilde; states as the source of the luminescence observed in those studies.
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