Ultraviolet photolysis of formyl fluoride: the F+HCO product channel

The time-of-Eight spectrum of the H atoms resulting from photodissociation of gas phase HFCO molecules at 243.12 nm indicates a role for secondary pho tolysis of HCO((X) over tilde) fragments arising via the F + HCO((X) over t ilde) dissociation channel. Analysis of this spectrum, and of earlier photo fragment translational spectroscopy results obtained at a number of neighbo uring wavelengths in the range 218.4-248.2 nm, allow estimation of an upper limit for the C-F bond dissociation energy: D-0(F-CHO) less than or equal to 482 kJ mol(-1). HCO((X) over tilde) fragments are deduced to be amongst the primary products of HFCO photolysis at all wavelengths lambda less than or equal to 248.2 nm, indicating that any energy barrier in the F-C bond f ission channel [measured relative to the asymptotic products F(P-2) + HCO(( X) over tilde)] must be small. This observation is considered in the light of available knowledge regarding the potential energy surfaces for the grou nd ((X) over tilde(1)A') and first excited singlet ((A) over tilde(1)A ") a nd triplet ((a) over tilde 3A ") states of HFCO; the available evidence all points to radiationless transfer and subsequent dissociation on the triple t surface as the mechanism for the deduced F-C bond fission.