Knowledge Bank

Studies of a photo-excited H-tunneling reaction in acridine doped flourene have predicted the presence of a $B1$ intra-molecular promoting mode, with a "butterfly" like mode pattern around $100cm-1$ in $flourene1$. Published polarized IR and Raman $spectra2$ have not shown candidates for such a mode. Raman Spectra are taken at pressures up to 35 kbar with hopes to identify it. Upon compression a mode is observed, at $98cm-1$ with a pressure of 3 kbar, which is considerably more sensitive to pressure than the phonon mode which obscures it at ambient pressure. Polarized Raman studies further identify this mode as having $B1$ symmetry. The Gruneisen parameter of other modes are examined to corroborate conclusions based on the "butterfly" mode's assignment. Crystallographic considerations explain the hypersensitivity to pressure in light of the proposed mode pattern. Results are compared with a recently published Normal Coordinate $Analysis3$.