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Departmental Colloquium

Stark and Zeeman Spectroscopy of Open Shell Molecular Complexes in Helium Nanodroplets  
Guest Speaker
Prof. Gary E. Douberly  
Guest Affiliation
University of Georgia, Department of Chemistry  
Thursday, September 1, 2016 3:30 pm - 4:30 pm  
Physics Auditorium (Rm 202)  
Pyrolytic decomposition of tert-butyl hydrogen peroxide has proven to be an efficient source for doping helium droplets with the hydroxyl radical (OH). Several OH containing molecular complexes have been stabilized in helium droplets following the sequential pick-up of OH and a closed shell molecular species. We have probed the geometric and electronic structures of these systems with infrared laser Stark and Zeeman spectroscopy, employing homogenous DC electric and magnetic fields applied to the laser-droplet beam interaction zone. For example, the T-Shaped OH—C2H2 complex has been probed via excitation of the OH and antisymmetric CH stretch modes. Partial quenching of orbital angular momentum upon complex formation results in parity splitting of rotational levels, which is fully resolved in the helium droplet spectra. A model Hamiltonian for the Stark effect for systems exhibiting partially quenched electronic angular momentum is employed to extract from experimental Stark spectra the permanent electric dipole moment for this system. Moreover, a model Zeeman Hamiltonian is derived, which allows for an analysis of coupling of the partially quenched electronic angular momentum to the external magnetic field and the associated gL and gS factors, which are apparently unaffected by the helium solvation environment. An IR-IR double resonance experiment with picosecond time resolution is proposed that will allow for an investigation of vibrational energy flow, vibrational pre-dissociation, and vibrational excitation-induced reaction in systems of this type.