Inter-band B(E1) Strengths in Heavy Nuclei based on the Proxy-SU(3) Scheme

Rotational bands of positive and negative parity are frequently found experimentally in heavy deformed even-even nuclei along with their corresponding $E2$ intra-band and $E1$ inter-band transitions. In $SU(3)$ symmetry-based models, calculating the $B(E2)$ strengths is relatively straightforward due to the relation between the $E2$ operator and the quadrupole generator of the algebra. However, calculating the $B(E1)$ strengths is a more difficult task, requiring computations involving the shell-model expansion of the dipole operator and multi-shell matrix elements. In this work the $E1$ operator is expanded in $SU(3)$ second quantization and applied to calculate the inter-band $B(E1)$ strengths of the isotope $^{224}$Th using the semi-microscopic algebraic quartet model (SAQM) based on the recently proposed proxy-$SU(3)$ scheme.