Feasibility of studying astrophysically important charged-particle emission with the variable energy $\gamma$-ray system at the Extreme Light Infrastructure -- Nuclear Physics facility

In the environment of a hot plasma, as achieved in stellar explosions, capture and photodisintegration reactions proceeding on excited states in the nucleus can considerably contribute to the astrophysical reaction rate. Usually, such reaction rates including the excited-state contribution are obtained from theoretical calculations as the direct experimental determination of these astrophysical rates is currently unfeasible. Future experiments could provide constraining information on the current reaction models which would improve the predictive power of the theoretical reaction rates. In the present study, experiments of photodisintegration with charged-particle emission leading to specific excited states in the residual nucleus are proposed. The expected experimental results can be used to determine the particle-transmission coefficients in the model calculations of photodisintegration and capture reactions. With such constrained transmission coefficients, the astrophysical reaction rates especially involving the excited state contributions can be better predicted and implemented in astrophysical simulations. In particular, ( γ ,p) and ( γ , α ) reactions in the mass and energy range relevant to the astrophysical p process are considered and the feasibility of measuring them with the ELISSA detector system at the future Variable Energy γ -ray (VEGA) facility at ELI-NP (Extreme Light Infrastructure - Nuclear Physics) is investigated. To this end, in a first step 17 reactions with proton emission and 17 reactions with α emission are selected and the dependence of calculated partial cross sections on the variation of nuclear property input is tested. The simulation results reveal that, for the ( γ ,p) reaction on twelve targets of 29 Si, 56 Fe, 74 Se, 84 Sr, 91 Zr, 96 , 98 Ru, 102 Pd, 106 Cd, and 115 , 117 , 119 Sn, and the ( γ , α ) reaction on five targets of 50 V, 87 Sr, 123 , 125 Te, and 149 Sm, the yields of the reaction channels with the transitions to the excited states in the residual nucleus, namely ( γ , X i ) with i (cid:54) =0, are relevant and even dominant. Therefore, these seventeen reactions are considered in the further feasibility study. For each of the seventeen photon-induced reactions, in order to attain the detectable limit of 100 counts per day for the total proton or α -particle yields, the minimum required γ -beam energies E low for the