Infrared Photodissociation Spectroscopic and Theoretical Study of Co(CO₂)_n⁺ Clusters

The mass-selected infrared photodissociation (IRPD) spectroscopy was utilized to investigate the interactions of cationic cobalt with carbon dioxide molecules. Quantum chemical calculations were performed on the Co(CO₂)_n⁺ clusters to identify the structures of the low-lying isomers and to assign the observed spectral features. All the Co(CO₂)_n⁺(n=2-6) clusters studied here show resonances near the CO₂ asymmetric stretch of free CO₂ molecule. Experimental and calculated results indicate that the CO₂ molecules are weakly bound to the Co⁺ cations in an end-on con guration via a charge-quadrupole electrostatic interaction. The present IRPD spectra of Co(CO₂)_n⁺ clusters have been compared to those of Ar-tagged species (Co(CO₂)_n⁺-Ar), which would provide insights into the tagging effect of rare gas on the weakly-bounded clusters.