Beta-delayed particle emission and collective rotations

TL;DR

This paper develops a formalism to analyze beta-delayed particle emissions in deformed nuclei, connecting nuclear rotational states and deriving selection rules, with applications to specific isotopes like $^{21}$Mg.

Contribution

It introduces a new theoretical approach to connect beta-delayed particle emissions with nuclear collective rotations and selection rules involving the $K$ quantum number.

Findings

Derived normalized matrix elements for particle emission between rotational states.

Established selection rules involving the $K$ quantum number.

Applied formalism to $^{21}$Mg, assigning new quantum numbers to $^{21}$Na states.

Abstract

Beta-delayed proton emission in the lower half of the sd-shell will involve deformed nuclei. We derive the normalized matrix element connecting emission of one particle from an initial rotational nuclear state to another final rotating state, and we extract selection rules involving the $K$ quantum number. The initial state is approximated as having a core identical to the final nuclear state. The formalism is then directly applicable to $\beta^+$-delayed proton decays of even-$Z$, odd-$N$ nuclei or $\beta^-$-delayed neutron decays of odd-$Z$, even $N$ nuclei. These beta-decay results are compared to the outcomes of possible transfer reactions. As an example the beta-delayed proton emission of $^{21}$Mg is considered, where new quantum numbers can be assigned to several states in $^{21}$Na.