ROTATION-TUNNELING ANALYSIS OF EXCITED-STATE PROTON TRANSFER IN DEUTERATED TROPOLONE
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Date
2011
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Ohio State University
Abstract
The origin band of the $\tilde{A}^{1}\rm{B}_{2}$ $-$ $\tilde{X}^{1}\rm{A}_{1}$ ($\pi^{*}\leftarrow\pi$) absorption system in monodeuterated tropolone (TrOD) has been probed with rotational resolution by applying polarization-resolved degenerate four-wave mixing (DFWM) spectroscopy under ambient, bulk-gas conditions. Judicious selection of polarization geometries for incident and detected electromagnetic waves alleviated intrinsic spectral congestion and facilitated dissection of overlapping transitions, thereby enabling refined rotational-tunneling parameters to be extracted for the $\tilde{A}^{1}\rm{B}_{2}$ ($\pi^{*}\pi$) manifold. A pronounced 2.14(5)\,$\wn$ bifurcation of rovibronic features is measured for the zero-point level of electronically excited TrOD, reflecting the presence of a substantial potential barrier along the O$-$D$\cdots$O $\longleftrightarrow$ O$\cdots$D$-$O reaction coordinate$ $\bf{130}$, 144304 (2009).} and representing nearly a ten-fold decrease in magnitude over the analogous tunneling-induced splitting for the parent (TrOH) isotopolog. The dependence of hydron-migration dynamics on internal degrees of freedom will be discussed in light of donor-acceptor displacements incurred by $\pi^{*}\leftarrow\pi$ electron promotion and structural effects accompanying selective isotopic modification of the tropolone molecular framework.
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Author Institution: Department of Chemistry, Yale University, P. O. Box 208107, New Haven, CT 06520-8107 USA