We study the vibrational relaxation and solvation dynamics in size-selected icosahedral Arn(NO-) at 300 K, where NO -(X~(3-)) is in v 1 and n 1-12, using a classical dynamics method and an interaction model consisting of detailed host-guest and host-host interactions. Two relaxation time scales are found: (i) the short-time (200 ps), in which rate is nearly independent of cluster size, and (ii) the ns scale, in which a slow energy transfer process occurs between NO- vibration and argon modes at a rate (～108 s-1) decreasing slightly from n 12 to 6 and rapidly from n 5 to 1 (～10 6 s-1). In Ar12(NO-), less than one-quarter of the host atoms sampled evaporate, nearly 60 of evaporation occurring within 200 ps caused by rapid energy transfer from NO- at short time. The fraction of evaporation decreases nearly exponentially with increasing evaporation time, but ～16 of evaporation still occurs on a time scale longer than 1 ns. Evaporation from one hemisphere of Ar _(12)(NO-) dominates the rest. Final cluster sizes commonly produced from the fragmentation of Ar_(12)(NO-) are n 6-11 (evaporation of 6-1 atoms) and n 12 (no evaporation).
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