Vibrational Dynamics and Dissociation of Ground- and Excited-State Clusters (Final Report)
- Univ. of Wisconsin, Madison, WI (United States)
Experimental studies of the dissociation of selectively excited molecules probe fundamental as-pects of chemical reactivity and molecular decomposition, and understanding excited-state decomposition dynamics presents both experimental and theoretical challenges. Photoexcitation of molecules from selec-tively prepared vibrational states is a proven means of studying electronically excited molecules and, in favorable cases, of controlling their dissociation pathways. This double resonance scheme, vibrationally mediated photodissociation, has uncovered new vibrational spectroscopy, determined bond strengths with high accuracy, altered excited state dissociation pathways, and revealed properties and couplings in elec-tronically excited states. Many practically important processes, such as excited state decomposition and bimolecular reaction, involve the intersection of two electronic states along one or more coordinates, and the resulting interaction often creates a conical intersection between the two states. These structures are both intriguing and significant because the evolution of molecules through conical intersections deter-mines the disposal of energy into dissociation fragments and the branching between different reaction pathways. This project is a systematic study of the photodissociation of vibrationally excited molecules and of their complexes with various adducts. This research uses vibrational and electronic excitation to deter-mine the influence of specific excitation on decomposition pathways. Previous studies of the dissociation of ammonia and phenol have shown that vibrational excitation can influence the formation of excited-state and ground-state products. The studies described here systematically study the photodissociation of vibrationally excited molecules and the behavior of their complexes in order to identify dissociation pathways, discover the factors that control the course of decompositions, and test theoretical models of the decomposition of energized molecules. The major accomplishments are a series of measurements on the ammonia dimer, the ammonia trimer, and the ammonia-aminophenol complex that reveal their vibra-tional predissociation dynamics and determine their binding energies. In addition, the research investi-gates the photodissociation of molecules in which multiple potentially energy surfaces play a role.
- Research Organization:
- Univ. of Wisconsin, Madison, WI (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB)
- DOE Contract Number:
- FG02-86ER13500
- OSTI ID:
- 1420781
- Report Number(s):
- DOE-UWISC-13500
- Country of Publication:
- United States
- Language:
- English
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