Bound-bound transitions in the emission spectra of Ba$^{+}$--He excimer

TL;DR

This study combines experimental and theoretical approaches to investigate the emission spectra of Ba$^{+}$--He excimers, revealing new spectral features and expanding the understanding of metal-helium quasimolecules with potential applications in high-resolution spectroscopy.

Contribution

It reports the discovery of new spectral features and the characterization of Ba$^{+}$(5$^{2}D_{J}$)He excimers, expanding the known family of metal-helium quasimolecules.

Findings

Identification of new spectral features in Ba$^{+}$--He emission spectra.

Assignment of features to electronic transitions between bound states.

Characterization of Ba$^{+}$(5$^{2}D_{J}$)He as a metastable excited complex.

Abstract

We present an experimental and theoretical study of the emission and absorption spectra of the Ba$^{+}$ ions and Ba$^{+\ast}$He excimer quasimolecules in the cryogenic Ba--He plasma. We observe several new spectral features in the emission spectrum which we assign to the electronic transitions between bound states of the excimer correlating to the 6$^{2}P_{3/2}$ and 5$^{2}D_{3/2,5/2}$ states of Ba$^{+}$. The resulting Ba$^{+}$(5$^{2}D_{J}$)He is a metastable electronically excited complex with orbital angular momentum $L$=2, thus expanding the family of known metal--helium quasimolecules. It might be suitable for high-resolution spectroscopic studies and for the search for new polyatomic exciplex structures.