Abstract
Gamow–Teller (GT) transitions are the most common weak interaction processes of spin–isospin ( σ τ ) type in atomic nuclei. They are of interest not only in nuclear physics but also in astrophysics; they play an important role in supernovae explosions and nucleosynthesis. The direct study of weak decay processes, however, gives relatively limited information about GT transitions and the states excited via GT transitions (GT states); β decay can only access states at excitation energies lower than the decay Q -value, and neutrino-induced reactions have very small cross-sections. However, one should note that β decay has a direct access to the absolute GT transition strengths B (GT) from a study of half-lives, Q β -values and branching ratios. They also provide information on GT transitions in nuclei far-from-stability. Studies of M 1 γ transitions provide similar information. In contrast, the complementary charge-exchange (CE) reactions, such as the ( p , n ) or ( 3He, t ) reactions at intermediate beam energies and 0°, can selectively excite GT states up to high excitation energies in the final nucleus. It has been found empirically that there is a close proportionality between the cross-sections at 0° and the transition strengths B (GT) in these CE reactions. Therefore, CE reactions are useful tools to study the relative values of B (GT) strengths up to high excitation energies. In recent ( 3He, t ) measurements, one order-of-magnitude improvement in the energy resolution has been achieved. This has made it possible to make one-to-one comparisons of GT transitions studied in CE reactions and β decays. Thus GT strengths in ( 3He, t ) reactions can be normalised by the β -decay values. In addition, comparisons with closely related M 1 transitions studied in γ decay or electron inelastic scattering [( e , e ′ )], and furthermore with “spin” M 1 transitions that can be studied by proton inelastic scattering [( p , p ′ )] have now been made possible. In these comparisons, the isospin quantum number T and associated symmetry structure in the same mass A nuclei (isobars) play a key role. Isospin symmetry can extend our scope even to the structures of unstable nuclei that are far from reach at present unstable beam factories.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.