A. Denis et al., SELECTIVE BEAM GAS-SPECTROSCOPY OF THE QUARTET SYSTEM OF NV, Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 98(1-4), 1995, pp. 65-68
Doubly excited states can be selectively produced by electron capture
from a gas or a metallic vapor target by low energy (a few keV/u) high
ly charged ions previously prepared in a metastable state. This method
has been applied to produce 2s nl and 2pnl NV quartet terms. Spectra
have been observed in the UV range (100-700 Angstrom).