Direct atomic scale observation of linkage isomerization of [As.sub.4][S.sub.5] clusters during the photoinduced transition of realgar to pararealgar

The reaction mechanism underlying the photoinduced linkage isomerization of discrete arsenic-sulfur clusters in the realgar form of tetraarsenic tetrasulfide to its pararealgar form was studied using Raman spectroscopy and infrared spectroscopy. The formation of intermediate [As.sub.4][S.sub.5] clusters and its linkage isomerization was observed.