Radiation from the Negative Lithium Ion

It is confirmed that the 3489-Å transition observed in beam-foil excited lithium spectra originates from the negative lithium ion. It is most probably the transition $1s2s2p^2{}_{}{}^5{}_{}{}^{}P-1s2\mathrm{}{p}^3{}_{}{}^5{}_{}{}^{}S_{}^{\circ }{}_{}{}^{}$, as suggested by Bunge. A new electric field acceleration technique provides identification of the charge state of the emitting ion. The decay curve is a cascade-free single exponential. The polarization and beam energy dependence of the light yield have also been measured. The transition has been identified in heavier isoelectronic ions.