STUDY OF HALOGEN CARBON-DIOXIDE CLUSTERS AND THE FLUOROFORMYLOXYL RADICAL BY PHOTODETACHMENT OF X(-)(CO2) (X=I,CL,BR) AND FCO2-

Photoelectron spectra have been measured for the anions X- (CO2), with X=I, Br, Cl, and F. The vibrationally resolved spectra show that I-(CO2), Br-(CO2), and Cl-(CO2) are primarily electrostatically bound clusters, although the charge-quadrupole interaction is strong enough to distort the CO2 molecule by as much as 10° [in CF(CO2)]. Ab initio calculations and electrostatic models are used to describe the geometry and bonding of these clusters. The photoelectron spectrum of FCO2 - is qualitatively different and shows transitions to both the X̃ 2B2 ground and the à 2A 2 first excited electronic states of the covalently bound FCO 2 radical. The previously unobserved à 2A 2 state is measured to lie 0.579 eV above the ground state. Vibrational frequencies are assigned with the assistance of ab initio calculations. The FCO2 heat of formation is determined to be ΔfH2980(FCO2)=-85.2±2. 8 kcal/mol. While both FCO2- and FCO2 are more strongly bound than the other halide-CO2 clusters, the C-F bonds are very weak relative to C-F bonds found in other halocarbon compounds. © 1995 American Institute of Physics.