ENERGY LEVELS OF THE SINGLY-IONIZED BERKELIUM - 249Bk II

       In the first report on the observation of the berkelium 249Bk spectrum in 1965, 20 lines were given without ion assignment (65.2), 10 of them being now interpreted as Bk II transitions. The spectra emitted by electrodeless discharge lamps contained several thousands of lines between 250 and 900 nm (67.3) and their systematic measurements led to a list of 1930 lines characterized by observed intensities, wavelengths, hyperfine widths and Zeeman structures, combining levels of Bk II for 219 of these lines (78.1).

    These data were completed by infrared observations by means of Fourier transform spectrometry at Laboratoire Aimé Cotton, and in the published list of the strongest 90 lines, only 6 of them were classified as Bk II (77.5).

    The preliminary analysis of (78.1) was revised and extended to include now 42 odd and 117 even levels of Bk II (87.2). Isotope shift data being still unavailable for berkelium, the configuration assignments are supported by empirical considerations on intensities and g-factors and on the Slater-Condon parametric study  of the ground configuration. As part of systematic investigations of 5fN7s configurations (80.4), 14 levels of 5f97s have been identified theoretically. The labelling of twelve levels 5f96d and four levels of 5f86s6p is empirical. In the even parity, some of the lowest levels of the 3 configurations 5f87s2, 5f86d7s and 5f97p have been found. In absence of hfs analysis of the lines, or Zeeman data (only 2 levels of Bk II have measured g-factors), the j-value is ambiguous for 26 % of the levels.