The effects of the spin-orbit and tensor interactions in nuclei

✍ Scribed by D.C Zheng; L Zamick

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 928 KB
• Volume: 206
• Category: Article
• ISSN: 0003-4916
• DOI: 10.1016/0003-4916(91)90223-u

✦ Synopsis

We devise a nucleon-nucleon interaction V, + XV,, + y V, to study the effects of the spinorbit and tensor interactions by varying x and y. For negative parity lp-lh states in 160, we find that in a TDA calculation, the weighted sum of the eigenenergies CJ(2J+ 1) L,E,(J, T) is zero for a pure two-body spin-orbit interaction or a pure tensor interaction. If a minor closed shell nucleus like i2C is taken as the core, the tensor interaction lowers the pllz singleparticle energy relative to P~,~. This is precisely opposite to what the two-body spin-orbit interaction does. For the l+ states in '%, a lp-lh diagonalization leads to a near collapse with E*( T= 0) -0.9 MeV and E*( T= 1) -3.7 MeV as compared with experiment (12.7 MeV for T=O and 15.1 MeV for T= 1). Only a full scalar shell model calculation brings these states up to a respectable energy. We find that in a full shell model calculation, the excitation energies of these l+ states are surprisingly insensitive to the spin-orbit interaction over a rather wide range of the parameter x and there does not appear to be any phase transition as we vary x. We reconsider the old problem of the effect of the spin-orbit and tensor interactions on the nearly vanishing Gamow-Teller matrix element %(J=O, T= 1) + 14N(J= 1, T= 0). We calculate the single-particle energies with the same interaction that is used for the residual particle-particle or particle-hole matrix elements. lb 1991 Academic Press. Inc.