Anharmonicity of internal atomic oscillation and effective antineutrino mass evaluation from gaseous molecular tritium \beta -decay

TL;DR

This paper investigates the anharmonic effects of atomic oscillations in gaseous molecular tritium and their impact on the systematic corrections needed for precise antineutrino mass measurements, comparing ab initio calculations with phenomenological models.

Contribution

It introduces an analysis of anharmonic atomic oscillations using Morse potential and compares these with existing ab initio calculations for tritium molecules.

Findings

Anharmonic corrections do not fully explain the differences with ab initio results.

Rovibrational band width is primarily due to zero-point atomic oscillations.

Morse potential analysis highlights limitations of harmonic models.

Abstract

Data analysis of the next generation effective antineutrino mass measurement experiment KATRIN requires reliable knowledge of systematic corrections. In particular, the width of the daughter molecular ion excitation spectrum rovibrational band should be known with a better then 1% precision. Very precise ab initio quantum calculations exist, and we compare them with the well known tritium molecule parameters within the framework of a phenomenological model. The rovibrational band width with accuracy of a few percent is interpreted as a result of the zero-point atomic oscillation in the harmonic potential. The Morse interatomic potential is used to investigate the impact of anharmonic atomic oscillations. The calculated corrections cannot account for the difference between the ab initio quantum calculations and the phenomenological model.