Real‐time dynamics of clusters. I. I₂X_n (n=1)

Vibrational predissociation of I₂X_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 I₂. Here, we report our study of I₂X(B,v′_i)^{k(v′_i,v′_f)} _→I₂(B,v′_f)+X. For I₂Ne, 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 I₂Ar (B,v_i), which undergo electronic and vibrational predissociation, the risetime of the nascent I₂ 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.