The hyperfine structures of 7,9Be− 2s2p2 4P
1/2,3/2,5/2
are investigated theoretically using the multiconfiguration Hartree–Fock and configuration
interaction methods. The effects of the hyperfine mixing between the fine-structure
J-levels
are discussed. The feasibility of some atomic spectroscopy
experiments, allowing determination of the 7Be
quadrupole moment from the observed hyperfine structure of the 7Be− negative
ion and from the present electronic parameters, is investigated. The Be 2s2p 3Po
electron affinity is monitored as a function of the orbital and configuration spaces
to assess the reliability of the wavefunctions of the neutral atom and the negative
ion. The theoretical value nicely converges towards the most recent theoretical
and experimental results.