The fluorine photodissociation dynamics in the first absorption band was co
mpletely characterised by detection of atomic fluorine using resonantly enh
anced multi-photon ionisation (REMPI). Jet-cooled parent molecules were exc
ited into the repulsive A(1)Pi(u) state by a 3 sigma(u) <-- 1 pi(g) electro
nic transition at 234 nm. Different intermediate excited states of atomic f
luorine are observed between 126500 and 128500 cm(-1) in a (3 + 1) ionisati
on process. Although the initially excited A(1)Pi(u) state exclusively corr
elates to electronic P-2(3/2) ground state atoms, the fragmentation also ge
nerates excited P-2(1/2) spin-orbit state atoms. The non-adiabaticity is fa
cilitated by the smallness of the spin-orbit splitting E-Omega(F) = 404.1 c
m(-1). Both time-of-flight and Doppler linewidth measurements agree with th
e calculated photofragments recoil velocity. (C) 1999 Elsevier Science B.V.
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