Disentangling the H₂E, F(¹Σ_g⁺) (v′=0−18)←X(¹Σ_g⁺)(v″=3−9)(2+1) REMPI spectrum via 2D velocity-mapped imaging

Abstract

We have measured the two-photon $EF\leftarrow X$ $(v^{″}=3-9)$ Resonance-Enhanced Multiphoton Ionization (REMPI) spectrum of H${}_2$ by producing the hydrogen molecule via photolysis of H${}_2$CO. H${}_2$ is produced with rovibrational energies up to 30,000 cm${}^{-1}$, at a maximum observed $(v^{″},J^{″})$ of (9,5). In the well-resolved jet-cooled H${}_2$CO spectrum, ortho and para H${}_2$ are selectively produced with near 100% selectivity. Over 470 REMPI transitions were identified in the EF−X band system, many of which have not been seen previously, including transitions to EF levels not yet accurately measured. Speed distributions were obtained for each REMPI transition using Velocity-mapped imaging, aiding in the assignment by providing a precise measurement of the internal energy of the H${}_2$ molecule.

GRAPHICAL ABSTRACT

Keywords:

• Velocity-mapped imaging
• VMI
• H² spectroscopy
• REMPI
• formaldehyde

Acknowledgments

Funding was provided by the Australian Research Council (DP190102013). MSQ was supported by an Australian Postgraduate Award.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Funding was provided by the Australian Research Council (DP190102013). MSQ was supported by an Australian Postgraduate Award.