Condensed excited states in beryllium

Results are presented from theoretical investigations of condensed excited states of beryllium by the Hartree–Fock method with allowance for the width of the atomic levels. It is shown that, during the excitation of a beryllium atom in the X-ray energy range, the 2p states split, unequal shift of one-electron energy levels and mixing of the 2s and 2p states at excitation energies of 10 and 14Ry are observed, and the atom is stabilized at energies higher than 6.7Ry. In the optical range of excitation energies, a condensed excited state of beryllium with a lifetime up to 0.1 fs is revealed.