Two Body Mesic Exchange Current Contribution to m1 Transitions and Magnetic Moments of Complex Nuclei.
In this thesis we study the one pion exchange (OPE) current contribution to nuclear magnetic moments and electro-magnetic transitions (M1). Almost all the previous theoretical and experimental work has been done for nuclei with closed shell (+OR-)1 nucleon. We examine relatively simple complex nuclei i.e., a nucleus with closed shell +2 nucleons (a,b) and a nucleus with closed shell +1 particle, 1 hole (a('-1)b). We use a pure j-j coupled shell model for calculation. First we review the theory of mesic currents and derive the OPEM1 operator. Then instead of studying OPE currents directly, we first analyze data from (a,b) and (a('-1),b) nuclei to find evidence of a two-body M1 transition operator. Information from a single nucleus is not sufficient for such an experimental analysis. We therefore, derive a linear relationship for the two-body M1 transition operator between a particle-particle (a,b) and a hole-particle (a(' -1)b) nucleus. Data from the two nuclei allow for a complete experimental analysis, which is most compactly represented by multipole coefficients. We find evidence of a two-body M1 transition operator. This operator may represent the effects of configuration mixing, meson exchange or both. We apply the method of analysis to the particle-hole pair ('38)Cl(a,b) and ('40)K(a('-1)b). We then rewrite the OPE transition operator in a suitable spherical tensor form. We derive a general formula to calculate the diagonal (moments) and off-diagonal (transitions) matrix elements of the OPE transition operator in j-j coupled (a,b) nuclei. The two-body OPE transition operator is a complicated operator. We consider one of the simplest terms and calculate its effects on the moments and M1 transition of ('38)C1. The effects seem to be too small to fill the gap between the experimental and the single-particle values. We estimate that when all the terms are added together, a 5%-10% correction would come from OPE currents.
- Pub Date:
- March 1982
- Physics: Nuclear