Delayed and direct cage exit in photodissociation ofCl2in solid Ar

The yield for photodissociation of ${\mathrm{Cl}}_2$ in solid Ar was measured experimentally as a function of photon energy and studied by molecular dynamics simulations. The results show that separation of the Cl fragments at low energies occurs by delayed exit (t≳3 ps) from the surrounding cage of Ar atoms. Above a photon threshold energy of ≳9.0 eV, there is a switchover to direct cage exit, in which the Cl impulsively knocks a cage atom out of its way. The results are a first demonstration of delayed cage exit and of changeover from delayed to direct exit in solid-state photolysis.