Photosensitivity of paramagnetic centers in radiolyzed solid hydrogen cyanide

Abstract

The photolysis of solid hydrogen cyanide and the effects of UV light on⁶⁰Co-γ-irradiated HCN at 77 K were studied using an ESR technique. As in the case of radiolysis, the HZ₂C=N radical formed due to “sticking” of the H atom to the triple bond of the HCN molecule is the main radical product of low-temperature HCN photolysis. The C=N⁻ radicals are accumulated at 77 K in insignificant amounts (≈3 %). It was established that radical and ionic products stabilized in y-irradiated HCN possess photochromism and under the action of UV light enter photochemical reactions leading to their decomposition. Upon photobleaching, the concentration of H₂C=N⁻ radicals first increases two- to threefold because of the decomposition of H₂C=N⁻ ions and then decreases. The presence of radicals and ions formed upon the low-temperature radiolysis of HCN broadens the optical absorption band of the system, and the boundary of the action spectrum shifts from 280 nm (for nonirradiated HCN) to the visible region at 400–440 nm.