Spectroscopy of Radiation-Induced Intermediates Formed by Phosphine Irradiation in Inert Matrices: Anionic Particles

Phosphine (PH) is one of the key inorganic molecules that arise from various biogenic compounds in terrestrial and planetary atmospheres. The action of ionizing radiation on phosphine molecules may result in the formation of charged particles, the characteristics of which are not sufficiently studied. In the present work, the vibrational spectra of isolated anions PH and PH which can be stabilized by the action of X-ray radiation on the systems PH/Ne and PH/Ar at 4.5 K have been experimentally obtained and characterized for the first time. The results obtained show that the frequencies of P-H valence vibrations in anionic particles are shifted to the red region relative to the frequencies of vibrations in the corresponding neutral molecules or radicals, which indicates the weakening of P-H bonds as a result of electron capture. Based on the analysis of the structure of the PH absorption bands in the neon matrix, it is suggested that this anion can arise by two different mechanisms - capture of thermalized electrons by PH...H pairs stabilized in one cell and dissociative capture of “hot” electrons by phosphine molecules.