$\beta$-delayed neutron spectroscopy of $^{85, 86}$As with MONSTER at IGISOL

TL;DR

This study measured beta-delayed neutron emissions from $^{85, 86}$As isotopes using advanced detection techniques, revealing new insights into neutron energy distributions and validating a novel unfolding methodology.

Contribution

The paper introduces an innovative Bayesian unfolding method combined with Monte Carlo simulations for analyzing beta-delayed neutron spectra, applied to $^{85, 86}$As isotopes.

Findings

Results for $^{85}$As agree with existing data.

Discovered higher neutron intensity at high energies in $^{86}$As.

Validated the new unfolding methodology.

Abstract

The $\beta$-delayed neutron emission in the $^{85, 86}$As $\beta$-decays has been measured at the Ion Guide Isotope Separator On Line facility of the Accelerator Laboratory of the University of Jyv\"askyl\"a. The complete $\beta$-decays have been studied with a complex setup that consists of a plastic scintillator for $\beta$-particles, MONSTER -- the MOdular Neutron time-of-flight SpectromeTER -- for neutrons, and a high-purity germanium and four LaBr$_3$ crystals for $\gamma$-rays. The $\beta$-delayed neutron energy distributions have been determined by unfolding the time-of-flight spectra with an innovative methodology based on the iterative Bayesian unfolding method and accurate Monte Carlo simulations. The results obtained for $^{85}$As are in excellent agreement with the existing evaluated data, validating the proposed methodology. In the case of $^{86}$As, a stronger neutron intensity at higher energies than previously predicted is discovered.