We propose and experimentally demonstrate that the trihydrogen cation (H3+) can be produced via single photoionization of the molecular hydrogen dimer (H4). Using near-infrared, femtosecond laser pulses and coincidence momentum imaging, we find that the dominant channel after single ionization of the dimer is the ejection of a hydrogen atom within a few hundred femtoseconds, leaving an H3+ cation behind. The formation mechanism is supported and well reproduced by an ab-initio molecular dynamics simulation. This is a new pathway of H3+ formation from ultracold hydrogen gas that may help explain the unexpected high abundance of H3+ in the interstellar medium in the universe.
@article{arxiv.2209.00203,
title = {Observation and dynamic control of a new pathway of H$_3^+$ formation},
author = {Yonghao Mi and Enliang Wang and Zack Dube and Tian Wang and A. Yu. Naumov and D. M. Villeneuve and P. B. Corkum and André Staudte},
journal= {arXiv preprint arXiv:2209.00203},
year = {2022}
}