G. Barratt Park and Robert W. Field Chirped Pulse Fourier Transform Microwave Spectroscopy in Pulsed Uniform Supersonic Flows Chamara Abeysekera, James M. Oldham, Baptiste Joalland, Kirill Prozument, Lindsay N. Zack, and Arthur G. Suits Department of Chemistry, Wayne State University G. Barratt Park and Robert W. Field Department of Chemistry, Massachusetts Instiute of Technology Ian R. Sims Institut de Physique de Rennes, Université de Rennes

Reaction Dynamics Gives a molecular-level understanding of chemical reactivity How a reaction proceeds Predict outcomes Common techniques: state-selected REMPI velocity map imaging

Reaction Dynamics For larger and more complex systems: Lack of isomer- and vibrational level-specific information Unreliable branching ratios Products not always able to be inferred

Chirped Pulse Fourier Transform Microwave Spectroscopy Isomer and vibrational level specificity Definitive identification of species Broadband advantage

Instrumentation

Spectrometer (“CPUF”) 26 – 40 GHz 60 – 90 GHz

Spectrometer

CP-FTMW-PUSF as a probe of nascent vibrational distributions t = 10 ms x5 v population 0.09 1 0.23 2 0.56 3 0.06 4 Brouard et al. (2004) JCPA, 108, 7965 Twelve sequential chirps plus FIDs are collected with 5 µs intervals. The nascent distribution is obtained initially and the quick relaxation to the v = 0 state is shown CP-FTMW-PUSF as a probe of nascent vibrational distributions t = 65 ms

C2H3CN HC3N (v, J) + H2 193 nm

Conclusions and Future Directions CPUF can be used to probe photochemistry Nascent product vibrational distributions can be investigated Bimolecular reactions next: Cl + alkenes Criegee intermediates and QOOH

Conclusions and Future Directions SOCl2 + C3H6 (analysis in progress)

Acknowledgements Prof. Arthur G. Suits (WSU) Prof. Robert W. Field (MIT) Prof. Ian R. Sims (Rennes) Suits, Field, and Sims Groups