Angular bremsstrahlung during $\alpha$-decay, emission from the internal region and unified formula of the bremsstrahlung probability

TL;DR

This paper develops a unified formalism for angular bremsstrahlung during alpha decay, providing a model that agrees well with experimental data and introduces a formula linking bremsstrahlung probability to nuclear properties.

Contribution

It presents a unified multipole and dipole formalism for bremsstrahlung in alpha decay and proposes a formula relating emission probability to nuclear parameters and Q-value.

Findings

Good agreement with experimental data for $^{210}$Po, $^{214}$Po, and $^{226}$Ra.

Internal well emission is significant in the dipole approach.

Proposed a universal formula for bremsstrahlung probability based on nuclear properties.

Abstract

Model of angular bremsstrahlung of photons emitted during $\alpha$-decay is presented. A special emphasis is given on development of unified formalism of matrix elements in the dipole and multipolar approaches. A probability of the emission of photons calculated on the basis of the multipole model without any normalization on experimental data (i. e. in absolute scale) is found at $90^{\circ}$ of the angle $\vartheta_{\alpha\gamma}$ between directions of motion of the $\alpha$-particle (with its tunneling under barrier) and emission of photons to be in a good agreement with the newest experimental data for the $^{210}{\rm Po}$, $^{214}{\rm Po}$, and $^{226}{\rm Ra}$ nuclei. The spectrum for $^{244}{\rm Cm}$ is found at $\vartheta_{\alpha\gamma} = 25^{\circ}$ to be in satisfactory agreement with high limit of errors of experimental data of Japanese group. A comparative analysis for the spectra calculated for $^{210}{\rm Po}$ by the multipole and dipole approaches in the absolute scale and with normalization on experimental data is performed. The emission of photons from the internal well in the dipole approach is found to be not small while the multipolar approach does not show such a strong dependence. Distribution of the bremsstrahlung probability on the numbers of protons and nucleons of the $\alpha$-decaying nucleus in selected region close to $^{210}{\rm Po}$ is obtained. An unified formula of the bremsstrahlung probability during the $\alpha$-decay of arbitrary nucleus expressed directly through the $Q_{\alpha}$-value and numbers $A_{p}$, $Z_{p}$ of nucleons and protons of this nucleus is proposed.