The tunneling-split origin band of the tropolone (A) over tilde B-1(2)-(X) over tilde (1)A(1) (pi*<--pi) absorption system was interrogated under ambient, bulk-gas conditions by exploiting high-resolution degenerate four-wave mixing techniques. The inherent complexity of this spectral region was alleviated by performing polarization-resolved measurements, with judicious selection of transverse characteristics for the incident and detected electromagnetic fields enabling rovibronic transitions to be discriminated according to their attendant changes in rotational angular momentum, DeltaJ. Quantitative simulation of recorded data sets showed the vibrationless level of the electronically excited state to be bifurcated by Delta(0)((A) over tilde)=19.846(25) cm(-1), representing a factor of 20 increase in proton-transfer efficiency over the corresponding level of the ground electronic state. Spectroscopic parameters extracted for the 0(+) and 0(-) manifolds of (A) over tilde B-1(2) tropolone yield unexpectedly large values of the inertial defect, DeltaI(0+)((A) over tilde)=-0.802(86) amu Angstrom(2) and DeltaI(0-)((A) over tilde)=-0.882(89) amu Angstrom(2), strongly suggesting that a loss of molecular planarity accompanies the pi*<--pi electron promotion. These results, as well as complementary information deduced for interloping hot-band resonances, are discussed in terms of the unique structural and dynamical properties exhibited by tropolone and related proton-transfer species. (C) 2004 American Institute of Physics.