Matrix-Isolation Study of the Vacuum-Ultraviolet Photolysis of Chloroform. Infrared Spectra of the CCl3+, HCCl2+, and HCCl2− Molecular Ions

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Abstract
Photolysis of samples of HCCl3 isolated in an argon matrix at 14°K using 1216‐Å radiation leads not only to the isolation of a high yield of CCl3, but also to the photoionization of CCl3, resulting in the stabilization of a sufficient concentration of CCl3+ for direct infrared spectroscopic identification. The assignment of still other infrared absorptions which appear in this system to negatively charged species has been confirmed by experiments in which a small concentration of an alkali metal atom is also present in the matrix, providing a photoelectron source. When matrix‐isolated HCCl3 is subjected to photolysis by 1067‐Å argon resonance radiation, very little CCl3 is produced, but HCCl2, HCCl2+, and the same negatively charged species are stabilized in significant concentration. Studies of chloroform samples enriched in carbon‐13 and of DCCl3 samples have provided support for these identifications and have yielded data necessary for obtaining several of the force constants of these species. The infrared spectrum of the negatively charged species can most satisfactorily be explained by postulating that dissociative electron attachment to chloroform occurs, resulting in the stabilization of HCCl2− in the matrix environment.