Parity-nonconservation effect in the helicities of conversion electrons accompanying the (5/2)? → (5/2)+ nuclear transition in the 229Pa nucleus

The ground state of the ²²⁹Pa nucleus is a 5/2^± doublet with a splitting energy of 220±50 eV. Such levels are peculiar to nuclei in the mass region around A=225 that are characterized by octupole deformations. A direct observation of P-odd effects in this system is of great interest because this can furnish information about the parity-nonconserving nucleon-nucleon potential. The transition between the two doublet states of opposite parities proceeds predominantly through internal conversion; therefore, P-odd mixing can be explored by studying the helicities of the conversion electron. It is shown that the helicities of the 6s _1/2, 6p _1/2, and 6p _3/2 conversion electrons are about 1%, which makes it possible to perform experiments aimed at determining the parameters of the effective parity-nonconserving nuclear potential.