Spectrum of the negative Be ion

The existence of Be^- is established from electron correlation calculations which include one-, two-, three-, and four-orbital excitations. The discrete spectrum of Be^- consists of three states: 1s²2s2p² ⁴P, 1s²2p³ ⁴Sᵒ, and 1s2s2p³ ⁶Sᵒ. The ⁴Sᵒ-⁴P transition offers the possibility of experimental detection of Be^-, e.g., by beam-foil methods. The theoretical wavelength and probability for the transition are λ=2671 {} and A=0.67×10⁹ sec^-1, respectively.