Relativistic and QED effects in the fundamental vibration of T$_2$

TL;DR

This study measures the fundamental vibrational transition in T$_2$ molecules with high precision, enabling the extraction of relativistic and QED effects, and significantly improves measurement accuracy over previous work.

Contribution

It provides the first high-precision measurement of T$_2$ vibrational splitting, allowing for detailed tests of relativistic and QED effects in molecules beyond hydrogen.

Findings

Achieved a fifty-fold improvement in measurement accuracy.

Extracted relativistic and QED contributions to T$_2$ transition energies.

Demonstrated the use of high-resolution spectroscopy for radioactive molecules.

Abstract

The hydrogen molecule has become a test ground for quantum electrodynamical calculations in molecules. Expanding beyond studies on stable hydrogenic species to the heavier radioactive tritium-bearing molecules, we report on a measurement of the fundamental T$_2$ vibrational splitting $(v= 0 \rightarrow 1)$ for $J=0-5$ rotational levels. Precision frequency metrology is performed with high-resolution coherent anti-Stokes Raman spectroscopy at an experimental uncertainty of $10-12$~MHz, where sub-Doppler saturation features are exploited for the strongest transition. The achieved accuracy corresponds to a fifty-fold improvement over a previous measurement, and allows for the extraction of relativistic and QED contributions to T$_2$ transition energies.