Dissociation Dynamics of Nitrogen Rich Cyclic Compounds

The photophysics and photochemistry of the nitrogen-rich compounds diazomethane and diazirine were studied both experimentally and theoretically following excitation in the ultraviolet. These molecules are locally stable on their ground potential energy surfaces, but they contain large amounts of nuclear potential energy that can be unleashed upon photoexcitation. Methods for generating these compounds in supersonically cooled molecular beams were developed to facilitate the experimental studies. Several Rydberg states of diazomethane were characterized experimentally and assigned on the basis of theoretical calculations. Couplings among the Rydberg states and other Rydberg and valence states were analyzed experimentally and the lifetimes of the excited states were estimated. Two-photon excitation of diazirine accessed an excited valence state that dissociated promptly to give CH radicals. A unique mechanism involving isomerization to isodiazirine was proposed to explain this unexpected result. Other excited states were assigned and characterized by high-level electronic structure calculations. The diazirine ion was found to be unstable and weakly bound, as opposed to the stable cation of diazirine. On the basis of this work, a revision to the heats of formation of diazirine and diazomethane was suggested. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 17 MAY 2010 2. REPORT TYPE 3. DATES COVERED 4. TITLE AND SUBTITLE Dissociation Dynamics of Nitrogen Rich Cyclic Compounds 5a. CONTRACT NUMBER