Bound-bound transitions in the emission spectra of Ba+-He excimer

We present an experimental and theoretical study of the emission and absorption spectra of the Ba+ ions and Ba+*He excimer quasimolecules in the cryogenic Ba-He plasma. We observe several 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.