Nonequilibrium effects in (alpha)-particle-induced reactions in Cs and I

The excitation functions for the reactions 127I(alpha,n)130Cs, 127I(alpha,2n)129Cs, 127I(alpha,4n)127Cs,133Cs(alpha,2n)135La, and 133Cs(alpha,4n)133La have been measured up to 50 MeV alpha-particle energy using the stacked-foil activation technique and Ge(Li) gamma-ray spectroscopy. The measured cross sections were compared with theoretical calculations considering equilibrium as well as the pro-equilibrium geometry-dependent hybrid models of Blann. The high-energy tails of the excitation functions show a substantial contribution from pre-equilibrium emission. A general agreement is observed between the experimental results and theoretical predictions with an initial exciton configuration n0 = 4(2n + 2p + 0h).