# Comment on "Hypersharp Resonant Capture of Neutrinos as a Laboratory Probe of the Planck Length"

## TL;DR

This paper critiques a proposed method for observing hypersharp neutrino resonant capture, arguing that practical issues like lattice inhomogeneities and relaxation processes prevent achieving the claimed natural linewidth in the 3H/3He system.

## Contribution

The authors provide a detailed critique of prior claims, highlighting physical and material limitations that challenge the feasibility of hypersharp neutrino resonance experiments.

## Key findings

- Lattice inhomogeneities hinder natural linewidth achievement.
- Relaxation processes prevent motional averaging of neutrino emission.
- Differences in lattice-deformation energies reduce phononless emission.

## Abstract

In Phys. Rev. Lett. 102, 091804 (2009) [arXiv:0903.0787], R.S. Raghavan claims that due to motional averaging by lattice vibrations, 18.6 keV electron antineutrinos emitted/captured without recoil from 2-body decay in the 3H/3He system embedded in Nb metal will be observable with natural width. In this comment we argue that 1) stochastic relaxation processes and 2) inhomogeneities in the metal matrices will prevent the generation of antineutrinos with natural width in the 3H/3He system, 3) the different lattice-deformation energies of 3H and 3He in the Nb matrix will drastically decrease the fraction of phononless emission/detection of antineutrinos, 4) the age itself of the 3H source does not affect the linewidth.