State and energy characterisation of fluorine atoms in the A band photodissociation of F2

The fluorine photodissociation dynamics in the first absorption band was completely characterised by detection of atomic fluorine using resonantly enhanced multi-photon ionisation (REMPI). Jet-cooled parent molecules were excited into the repulsive A 1Πu state by a 3σu←1πg electronic transition at 234 nm. Different intermediate excited states of atomic fluorine are observed between 126500 and 128500 cm−1 in a (3+1) ionisation process. Although the initially excited A1Πu state exclusively correlates to electronic 2P3/2 ground state atoms, the fragmentation also generates excited 2P1/2 spin–orbit state atoms. The non-adiabaticity is facilitated by the smallness of the spin–orbit splitting EΩ(F)=404.1 cm−1. Both time-of-flight and Doppler linewidth measurements agree with the calculated photofragments recoil velocity.