Knowledge Bank

The first $\pi \ast \leftarrow \Pi$ electronic transition of fluorobenzene and two deutered isotopes has been photographed and vibrational analysis performed. The bulk of the intensity present in the spectra falls into three classes: 1. the origin band, which presents an allowed $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}B2\leftarrow 1A1$ transition 2. totally symmetric vibrations, active in both cold and hot bands 3. sequence bands of out-of-plans vibrations. Values for some excited state frequencies are presented, and the anomalous behavior of vibration 6a is discussed. The information obtained from this analysis is then correlated with the excited state geometry of fluorobenzene.