Real-time dynamics of clusters. I. I_2X_n(n=1)

Vibrational predissociation of I_2X_n (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 v′_i by monitoring the rise of nascent I_2. Here, we report our study of I_2X(B,v′_i)k(v '_i,v′_f) →I_2(B,v′_f)+X. For I_2Ne, the values of τ=k^(−1)(v'_i,v′_f) decrease nonlinearly from 216 ps for v'_i=13 to 53 ps for v′_i=23. For I_2Ar (B,v'_i), which undergo electronic and vibrational predissociation, the risetime of the nascent I_2 is found to be 70 ps when v′_i=18 and 77 ps when v'_i=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