Predicted spectrum of atomic nobelium

The electronic spectrum of atomic nobelium (element 102) is calculated in preparation for a planned experiment. The intermediate-Hamiltonian (IH) coupled-cluster method is applied to the ionization potential and excitation energies of the atom, using a large basis set (37s 31p 26d 21f 16g 11h 6i) and correlating the outer 42 electrons. All the levels studied are obtained simultaneously by diagonalizing the IH matrix. The rows and columns of this matrix correspond to all excitations from correlated occupied orbitals to virtual orbitals in a large P space (8s 6p 6d 4f 2g 1h), and the matrix elements are "dressed" by including excitations to the higher virtual orbitals (Q space) at the coupled cluster singles-and-doubles level. Lamb shift corrections are included. The accuracy is assessed by applying the same method to ytterbium, the lighter homologue of No. The calculated ionization potential of Yb is within 3 meV of experiment, and the average error in the lowest 20 excitation energies of the atom is 300 cm-1. Nobelium is the heaviest element for which a reliable semiempirical estimate of the ionization potential exists, 6.65 (7) eV; the calculated value of 6.632 eV is in excellent agreement. Transition amplitudes are obtained from an extensive relativistic configuration interaction calculation. The outstanding feature of the predicted nobelium spectrum is a very strong line at 30 060 cm-1, with an amplitude A=5.0× 108 s-1, corresponding to the 7s7p P11 →7 s2 S01 transition. Putting the error limit conservatively at 0.1 eV, we predict a strong feature in the No spectrum at 30 100±800 cm-1.