Ultraviolet absorption spectra, structure, vibrations, and theoretical calculations of 2-fluoro- and 3-fluoropyridine in their electronic excited states

The ultraviolet absorption spectra of 2-fluoropyridine (2FPy) and 3-fluoropyridine (3FPy) vapors have been collected and assigned. For 2FPy about 150 bands were observed for the transitions to the vibronic levels of the S(π, π∗) state at 38 030.4 cm−1. Both single quantum jump transitions to A′ states and double quantum jumps transitions involving A″ modes were observed allowing most of the vibrational frequencies in the excited state to be identified. For 3FPy more than a hundred absorption bands associated with the S(n, π∗) state at 35 051.7 cm−1 and about 40 broad bands associated with the S(π, π∗) state at 37 339 cm−1 were observed. The experimental work was complemented by ab initio calculations.