The Effect of Charge Symmetry on Nuclear Reactions

Abstract

For a charge symmetric nuclear Hamiltonian, the operator which changes neutrons into protons and protons into neutrons (charge parity operator) commutes with the Hamiltonian and is therefore a constant of the motion. Since the charge parity operator anticommutes with the "3" component of the total isotopic spin, for nuclei with $T_3=0\mathrm{}$ (self-conjugate nuclei) the charge parity is a good quantum number and in the absence of degeneracy the eigenstates of such nuclei have either odd or even charge parity. This leads to strong selection rules in nuclear reactions involving self-conjugate nuclei in the initial and final states which may reasonably be invoked to explain recent experimental results on such reactions. Since states of even total isotopic spin have even charge parity and states of odd total isotopic spin have odd parity, the selection rules arising from charge symmetry often coincide with those of charge independence and in such cases a definitive test of the charge independence hypothesis by the use of these selection rules is impeded. Some other applications of the charge symmetry principle are discussed.