PARAMAGNETIC CENTERS TRAPPED IN SOLID HYDROGEN-CYANIDE UPON GAMMA-IRRADIATION

Buildup of paramagnetic centers was found to occur in high radiation y ield (G = 8 species/100 eV) upon low-temperature (77 K) radiolysis of hydrogen cyanide. The C=N radicals produced via abstraction of H atom from the neutral molecule and H2C=N radicals formed via addition of at omic hydrogen to HCN molecules were identified by EPR spectra. The mai n radical species is H2C=N, the radicals C=N due to abstraction are ac cumulated in low amounts. In addition to these two known species, the buildup of paramagnetic centers (approximate to 25% of the total) exhi biting a doublet EPR spectrum (line splitting Delta H = 8.2 mT, intens ity ratio 1 : 1) was observed. These species could not be unambiguousl y identified. On warming HCN samples up to room temperature, paramagne tic centers having a conjugated double bond system were characterized as polyene radicals by EPR spectra displaying single EPR lines of vary ing (from 2.2 to 0.3 mT) width and having g = 2.0023. Their presence i s indicative of the formation of a polymer on warming up of gamma-irra diated HCN; the polymer yield at a dose of 800 kGy was approximate to 2.5%.