15min:

KATHRYN CHEW, DEACON J. NEMCHICK, JOHN E. WOLFF AND PATRICK H. VACCARO, Department of Chemistry, Yale University, P. O. Box 208107, New Haven, CT 06520-8107 USA.

The origin band of the A¹B₂ - X¹A₁ ( ^* ) 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 A¹B₂ ( ^* ) manifold. A pronounced 2.14(5) cm^-1 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 O O D-O reaction coordinate 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 ^* electron promotion and structural effects accompanying selective isotopic modification of the tropolone molecular framework.