THE INVESTIGATION OF THE (CO)(2)(+) ION BY DISSOCIATIVE IONIZATION OFARGON CARBON MONOXIDE CLUSTERS/

The formation of (CO)(2)(+) ion has been investigated by the dissociat ive ionization of Ar(CO)(2) clusters in a threshold photoelectron phot oion coincidence experiment. The kinetic energy released (KER) in the reaction Ar(CO)(2)(+)-->(CO)(2)(+)+Ar has been measured as a function of the internal energy of the Ar(CO)(2)(+) ion. The comparison between the experimental KER and the statistically expected KER allows one to extrapolate back to zero KER which corresponds to the thermochemical threshold for the formation of (CO)(2)(+). The ionization potential (I P) of (CO)(2) is determined to be 12.24+/-0.15 eV. This leads to a bin ding energy of the (CO)(2)(+) of 1.80 eV one of the strongest known fo r any ionized van der Waals dimer. Our data are in line with a trans p lanar structure of the CO dimer ion as suggested by our ab initio calc ulations at the CI level. (C) 1995 American Institute of Physics.