Results from excitation of the 3 mode at 2546 cm -1 are shown in Fig. . The top panel shows IR-off (black) and IR-on spectra (red), the middle panel is the difference spectrum, and the bottom panel shows a harmonic FC simulation starting from the anion 3=1 level. Clearly, the difference spectrum is much more complex than the ground state spectrum. Moreover, it is in poor agreement with the FC simulation, which predicts a few 3 sequence band transitions (3 1 1 , etc.) above the vibrational origin and no transitions below the origin. The experimental difference spectrum, in contrast, shows many small features below the origin, and a comparison to the FC simulation suggests that each 3 sequence band appears to be split into four closely spaced transitions.