Vibrational predissociation of I2Xn (X=Ne, Ar) van der Waals clusters are studied in real‐time using picosecond pump–probe (LIF) and molecular beam techniques. The state‐to‐state rates of vibrational predissociation are measured for specific vibrational levels vi by monitoring the rise of nascent I2. Here, we report our study of I2X(B,vi)k(vi,vf)I2(B,vf)+X. For I2Ne, the values of τ=k−1(vi,vf) decrease nonlinearly from 216 ps for vi=13 to 53 ps for vi=23. For I2Ar (B,vi), which undergo electronic and vibrational predissociation, the risetime of the nascent I2 is found to be 70 ps when vi=18 and 77 ps when vi=21. A number of theoretical models for vibrational predissociation (the energy‐gap law, the momentum‐gap law, quantum and classical calculations) are compared with our experimental results in an attempt to understand the key features of the dynamics and the potential energy surface.

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