The cage-induced stabilization of fragments in excited electronic states following the UV-dissocn. of ICN in cryogenic matrixes is discussed. Emission spectra recorded upon ~A-band excitation of ICN in solid Ne, Ar and Kr exhibit a long progression of broad bands due to a weakly bound electronically excited state, presumably one of the low-lying triplet states 3P1 or 3P2 of ICN. A lifetime anal. favors the 3P2 state. Mol. dynamics with quantum transitions (MDQT) simulations were conducted on 6 coupled electronic potential energy surfaces in a matrix of 498 Ar atoms. Although a complete potential energy surface for the 3P2 state is not available, it is similar to 3P1. Only the 6 available [3P1 (A',A''), 3P0+, 1P1 (A',A''), X1S+] ab initio electronic potential energy surfaces were considered. The results predict a 2% probability of stabilization in the shallow min. of the triplet excited state. The mol. adopts a linear ICN configuration with a mean value of the I-CN distance far away from the absorption Franck-Condon region. The simulations also deliver insight into the mechanism of cage-induced population trapping in excited state surfaces, which is not accessible in the gas phase. [on SciFinder (R)]