The H2-H2 molecular dimer is of fundamental importance in the study of chemical interactions because of its unique bonding properties and its ability to model more complex systems. The trihydrogen cation H3+ is also a key intermediate in a range of chemical processes in interstellar environments, such as the formation of various organic molecules and early stars. However, the unexpected high abundance of H3+ in molecular clouds remains challenging to explain. Here using near-infrared, femtosecond laser pulses and coincidence momentum imaging, we find that the dominant channel after photoionization of a deuterium molecular dimer (D2-D2) is the ejection of a deuterium atom within a few hundred femtoseconds, leading to the formation of D3+. The formation mechanism is supported and well-reproduced by ab initio molecular dynamics simulations. This pathway of D3+ formation from ultracold D2-D2 gas may provide insights into the high abundance of H3+ in the interstellar medium.
© 2023. The Author(s), under exclusive licence to Springer Nature Limited.