Comment on "138La-138Ce-136Ce nuclear cosmochronometer of the supernova neutrino process"

TL;DR

This paper critiques a proposed nuclear cosmochronometer based on La-Ce isotope ratios, providing evidence against a hypothesized low-energy 1+ state in 138La that would affect its reliability.

Contribution

It offers experimental evidence refuting the existence of a low-energy 1+ state in 138La, challenging the validity of the proposed cosmochronometer.

Findings

No evidence for the hypothesized 1+ state in 138La from recent experiments.

The proposed cosmochronometer may be unreliable due to this missing state.

The study refutes a key assumption in the original chronometer proposal.

Abstract

The nuclear chosmochronometer suggested by Hayakawa et al. [Phys. Rev.C 77, 065802 (2008)] based on the 138La-138Ce-136Ce abundance ratio in presolar grains would be affected by the existence of a hitherto unknown low-energy 1+ state in 138La. Results of a recent high-resolution study of the 138Ba(3He,t) reaction under kinematics selectively populating 1+ states in 138La through Gamow-Teller transitions provides strong evidence against the existence of such a hypothetical state.