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

Abstract

Background: The ${}^{136}$Ba isotope is the daughter nucleus in ${}^{136}$Xe ${\hat{I}}^2{\hat{I}}^2$ 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 ${\hat{I}}^2{\hat{I}}^2$ 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.

16 pages, 15 figures, 1 table