# Level scheme of $^{153}$Sm obtained from $^{152}$Sm($n_{th}$,$\gamma$) reaction using $\gamma-\gamma$ coincidence spectrometer

## TL;DR

This study maps the detailed gamma-ray decay scheme of $^{153}$Sm formed via neutron capture, revealing new cascades and levels, and providing insights into its nuclear structure through gamma coincidence measurements.

## Contribution

The paper presents the first comprehensive level scheme of $^{153}$Sm from neutron capture, identifying new gamma transitions and levels, and assigning spins based on gamma cascade analysis.

## Key findings

- Detected 576 gamma transitions from 386 cascades.
- Identified 74 primary gamma transitions and 291 secondary transitions as new data.
- Tentatively assigned spin 3/2 to 53 intermediate levels.

## Abstract

The level scheme of the compound $^{153}$Sm nucleus formed via the $^{152}$Sm($n_{th}$,$\gamma$) reaction is studied by using the $\gamma-\gamma$ coincidence spectrometer at Dalat Nuclear Research Institute, Vietnam. All the gamma cascades, which correspond to the decays from the compound state to 12 final levels of 0 ($\frac{3}{2}^+$), 7.535 ($\frac{5}{2}^+$), 35.844 ($\frac{3}{2}^-$), 90.875 ($\frac{5}{2}^-$), 126.412 ($\frac{1}{2}^-$), 127.298 ($\frac{3}{2}^-$), 182.902 ($\frac{5}{2}^-$), 321.113 ($\frac{3}{2}^+$), 404.129 ($\frac{1}{2}^-$), 405.470 ($\frac{3}{2}^-$), 414.924 ($\frac{1}{2}^+$), and 481.088 ($\frac{3}{2}^+$) keV, have been measured. A total number of 386 cascades corresponding to 576 gamma transitions has been detected. Among these cascades, 103 primary gamma transitions together with their corresponding intermediate levels and 299 secondary transitions have been determined. In addition, 29 primary gamma transitions, 42 intermediate levels, and 8 secondary transitions have been found to be the same as those extracted from the ENSDF data. The remain 74 primary gamma transitions, 61 intermediate levels, and 291 secondary transitions are therefore considered as the new data. In particular, based on an assumption that most of the transitions are dipole, we have tentatively assigned the unique spin value of $\frac{3}{2}\hbar$ for 53 observed intermediate levels corresponding to the cascades from the compound state to the final ones of 7.535 ($\frac{5}{2}^+$), 90.875 ($\frac{5}{2}^-$), and 182.902 ($\frac{5}{2}^-$) keV, whereas the remain levels are assigned with the spin values in the range of $[\frac{1}{2},\frac{3}{2}]\hbar$...