# Observation of the $^7$H excited state

## TL;DR

This study reports the observation of an excited state in the unbound nucleus $^7$H, providing measurements of its energy levels and decay properties through a specific nuclear reaction experiment.

## Contribution

First experimental identification and energy measurement of the $^7$H excited state using a $^8$He beam and missing mass spectroscopy.

## Key findings

- $^7$H excited state observed at 6.5(5) MeV
- Indications of the $^7$H ground state at 2.0(5) MeV
- Low population cross section of about 10 μb/sr

## Abstract

The $^7$H system was populated in the $^2$H($^8$He,$^3$He)$^7$H reaction with a 26 AMeV $^8$He beam. The $^{7}$H missing mass energy spectrum, the $^{3}$H energy and angular distributions in the $^7$H decay frame were reconstructed. The $^7$H missing mass spectrum shows a peak which can be interpreted either as unresolved $5/2^+$ and $3/2^+$ doublet or one of these states at 6.5(5) MeV. The data also provide indications on the $1/2^+$ ground state of $^7$H located at 2.0(5) MeV with quite a low population cross section of $\sim 10$ $\mu$b/sr within angular range $\theta_{\text{cm}} \simeq 6^{\circ} - 30^{\circ}$.