Production of neutron-deficient nuclei around N = 126 by proton-induced spallation*

Abstract

Abstract Many isotopes of Np, Pu, Am, and Cm around the N = 126 shell still have not been produced in the laboratory. This study aims to investigate the cross sections and yields of the neutron-deficient nuclei of Np, Pu, Am, and Cm produced in the proton-induced spallations of transuranium elements. The isospin-dependent quantum molecular dynamics (IQMD) model is applied to study the dynamical process of reaction, and the subsequent decay process is simulated by the GEMINI++ model. The IQMD-GEMINI++ model is applied to calculate the cross section, kinetic energy, and angular distribution of the isotopic productions around N = 126. The Lindhand, Scharff, and Schiott theory is applied to calculate the energy loss of different heavy nuclei in the target material. A comparison between the data and the calculations shows that the IQMD-GEMINI++ model can reproduce the production cross sections of the neutron-deficient nuclei in spallation within approximately 1.5 orders of magnitude. The maximum cross section of the undiscovered isotopes of Np, Pu, Am, and Cm is about 10−5 mb, while the kinetic energies of the productions are all less than 16 MeV. The angular distribution shows that the emission direction of production is mostly at a backward angle. The range of production in the target is within the range of 10−7 to 10−5 cm. This range is the effective target thickness for the online identification of undiscovered isotopes. Based on the effective thickness of the target and assuming an intensity of 120 μA for the proton beam, the yields of the undiscovered neutron-deficient nuclei are calculated. Productions of the undiscovered isotopes of Np, Pu, Am, and Cm by the proton-induced spallations of transuranium elements are feasible. However, experimental techniques for online identification of neutron-deficient nuclei produced in proton-induced spallation should be developed.