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

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.