Anomalous Parity States of C¹³, N¹³and N¹⁴

Abstract

The low-lying anomalous parity states of C13 and N13 are shown to be well described in terms of the shell model states in which a positive-parity nucleon couples to a core which corresponds to C12 and its lowest two states are taken into account in the actual calculation. The Hamiltonian with a single-body spin-orbit interaction and a two-body central interaction is diagonalized among the above states and supplementary basic states. The latter basic states are necessary, in our method of treatment, to remove spurious states, which must not be contained in our wave functions. The center-of-mass correction is seen to have a very important effect on our results. The results for the energy spectra in C13 are found to be in fair agreement with the experiments: Especially we have succeeded in elucidating the reason why the lowest positive-parity level 1/2+ of C13 is observed at a very small excitation energy (3.08 Mev). The agreements with the experiments are also good on the Coulomb shifts between the isotopic doublets, on the reduced widths for the proton emission and on various kinds of radiative transitions. A similar method of calculation is performed to investigate the properties of the negative-parity states of N14, getting fair agreements with the experiments.