Evidence for Decreased Pairing Energies in Odd-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi></mml:math>Nuclei from Band-Crossing Frequencies

Abstract

An odd-even neutron-number dependence of the alignment frequency of the first pair of ${i}_{\frac{13}{2}}$ quasineutrons in rare-earth nuclei is established. This effect is explained by a reduction of the neutron pairing-correlation parameter ${\ensuremath{\Delta}}_{n}$ for odd-$N$ systems as compared to seniority-zero configurations in even-$N$ nuclei.