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

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.

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