Knowledge Bank

1,4-Fluorobenzyl alcohol (FBA) exhibits a number of closely spaced $(\sim 50cm-1)$ bands in its vibrationally resolved $S1\leftarrow S0$ electronic spectrum at $\sim 269$ nm, previously attributed to a $-CH2OH$ torsional mode. We report here a rotationally resolved study of the four members of this progression. All bands can be fit with rigid rotor Hamiltonians; a comparison of the parameters obtained from these fits shows that all bands belong to the same conformer. All bands exhibit a $\sim 300$ MHz splitting due to the torsion-rotation interaction. Band 3 and 4 also exhibit splitting (of $\sim 100$ and $\sim 800$ Mhz, respectively) due to interactions with other low energy vibrational modes. The nature of these modes and their possible participation in the energy relaxation pathways will be discussed.