dc.creator Dong, Feng en_US dc.creator Davis, Scott en_US dc.creator Nesbitt, David J. en_US dc.date.accessioned 2008-01-11T21:58:03Z dc.date.available 2008-01-11T21:58:03Z dc.date.issued 2005 en_US dc.identifier 2005-TJ-08 en_US dc.identifier.uri http://hdl.handle.net/1811/30629 dc.description Author Institution: JILA, University of Colorado, Boulder, CO 80309 en_US dc.description.abstract High-resolution infrared spectra of jet-cooled cyclopropyl radical are reported for the first time, specifically sampling the in-phase antisymmetric CH$_2$ stretch ($\nu_7$) vibration. In addition to yielding first precise gas phase structural information for this radical, the spectra reveal doubling due to quantum tunneling of the lone $\alpha$-CH with respect to the CCC plane, lift the degeneracy and generating lower (+) and upper (-) tunneling states. The bands clearly reveal intensity alternation (6:10 for even:odd Ka+Kc levels in the lower $\leftarrow$ lower and 10:6 in the upper $\leftarrow$ upper) due to H atom nuclear spin statistics, confirming that the tunneling transition state for cyclopropyl radical is of C$_{2v}$ symmetry. However, in addition to the two predicted vibrational bands (i.e. lower $\leftarrow$ lower and upper $\leftarrow$ upper), a third band is observed due to IVR mixing of the upper tunneling component ($\nu_7$) with a nearly isoenergetic dark state. From fractional populations in the ground and excited state, the tunneling splittings for cyclopropyl radical in the ground and excited ($\nu_7$) state are estimated to be 3.2$\pm{0.3}$ cm$^{-1}$ and 4.9$\pm{0.3}$ cm$^{-1}$, respectively. This indicates that stereoracemization of the $\alpha$-CH radical center is a very fast process (k=2.0x10$^{11}$ s$^{-1}$), and that the barrier decreases upon vibrational excitation of the CH$_2$ in-phase antisymmetric stretch. The barrier height for $\alpha$-CH inversion through the cyclopropyl plane is also extracted from the analysis of the tunneling dynamics with simple 1D potential energy surface. en_US dc.language.iso English en_US dc.publisher Ohio State University en_US dc.title SLIT DISCHARGE SPECTROSCOPY OF JET-COOLED CYCLOPROPYL RADICAL IN THE ANTISYMMETRIC CH$_2$ STRETCH ($\nu_7$) MANIFOLD: STRUCTURES, TUNNELING BARRIER AND INTRAMOLECULAR DYNAMICS en_US dc.type article en_US
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