Spectroscopy of states in $^{136}\rm{Ba}$ using the $^{138}\rm{Ba}(p,t)$ reaction

TL;DR

This study used the (p,t) reaction to map out 102 states in $^{136}$Ba, including 52 newly observed states, providing detailed spectroscopic data to inform nuclear models and neutrinoless double beta decay research.

Contribution

It presents the first comprehensive spectroscopic mapping of $^{136}$Ba states up to 4.6 MeV, including new state observations and clarified spin-parity assignments.

Findings

102 excited states observed in $^{136}$Ba

52 states reported for the first time

Spin-parity assignments made for 26 states

Abstract

Background: The $^{136}$Ba isotope is the daughter nucleus in $^{136}$Xe $\beta\beta$ decay. It also lies in a shape transitional region of the nuclear chart, making it a suitable candidate to test a variety of nuclear models. Purpose: To obtain spectroscopic information on states in $^{136}$Ba, which will allow a better understanding of its low-lying structure. These data may prove useful to constrain future $^{136}$Xe $\to$ $^{136}$Ba neutrinoless $\beta\beta$ decay matrix element calculations. Methods: A $^{138}\mathrm{Ba}(p,t)$ reaction was used to populate states in $^{136}$Ba up to approximately 4.6 MeV in excitation energy. The tritons were detected using a high-resolution Q3D magnetic spectrograph. A distorted wave Born approximation (DWBA) analysis was performed for the measured triton angular distributions. Results: One hundred and two excited states in $^{136}$Ba were observed, out of which fifty two are reported for the first time. Definite spin-parity assignments are made for twenty six newly observed states, while previously ambiguous assignments for twelve other states are resolved.