Chemical probing spectroscopy of H3+ above the barrier to linearity

TL;DR

This study used chemical probing spectroscopy to observe 17 new transitions of H3+ ions above the barrier to linearity, revealing extremely weak spectral lines and providing insights into the molecule's excited states.

Contribution

It reports the first observation of 17 previously unobserved transitions of H3+ ions above the barrier to linearity, including the weakest transitions detected to date.

Findings

Detected 17 new transitions above the barrier to linearity.

Some transitions are over five orders of magnitude weaker than fundamental bands.

Provided experimental data aligning with theoretical predictions.

Abstract

We have performed chemical probing spectroscopy of H3+ ions trapped in a cryogenic 22-pole ion trap. The ions were buffer-gas cooled to 55K by collisions with helium and argon. Excitation to states above the barrier to linearity was achieved by a Ti:Sa laser operated between 11300 and 13300 cm-1. Subsequent collisions of the excited H3+ ions with argon lead to the formation of ArH+ ions that were detected by a quadrupole mass spectrometer with high sensitivity. We report the observation of 17 previously unobserved transitions to states above the barrier to linearity. Comparison to theoretical calculations suggests that the transition strengths of some of these lines are more than five orders of magnitude smaller than those of the fundamental band, which renders them - to the best of our knowledge - the weakest H3+ transitions observed to date.