Knowledge Bank

The FTIR spectrum of tropolone(OH) vapor in the 1175 - 1700 $cm-1$ region is reported at 0.0025 and 0.10 $cm-1$ spectral resolutions. Estimates for the spectral doublet component separations for 11 fundamentals are based on the measurement of sharp Q branch peaks. The three highest of six $a1$ modes show splittings $\Delta v$ $\approx$ $\Delta 0$ (the known ZP splitting value), and four of the five observed $b2$ modes show splittings $\Delta v$ $\approx$ 0.90 $\Delta 0$. The remaining four splittings fall 4 to 14 % from $\Delta 0$, including $\Delta 8$ (nominal COH bending) = 1.10 $\Delta 0$. The data show that significant anharmonic behavior accompanies the mild perturbations of midrange vibrational excitations on the ZP tunneling mechanism. The results suggest the onset of fast IVR processes that can delocalize and smooth the imprint of the vibrational excitation energy on the ZP PES topography before the tautomerization process can occur. Further, the results suggest dynamical characteristics of the $b2$ modes include a damping effect on the tunneling process.