Photoabsorption structure in lanthanides: 5p subshell spectra of Sm I, Eu I, Dy I, Ho I, Er I, Tm I, and Yb I

Spectra of 7 lanthanide atomic vaours have been photographed between 300 and 1100 angstrom against the continuum from the Bonn 0.5 GeV electron synchrotron. Relative absorption cross-section plots are presented, showing strongly auto-ionized Rydberg series, identified principally as 5p$^{6}$ 4f$^{\text{q}}$ 6s$^{2}$-5p$^{5}$ 4f 6s$^{2}$ $n$d transitions. Spin-orbit splitting in the p$^{5}$ core (6.17 $\pm $ 0.03 eV for Yb I) dominates the structure for $Z$ = 66-70 and is relatively independent of $Z$. Broad, asymmetric resonances above the p$^{5}$ $^{2}$P$_{\frac{3}{2}}$ based limits, which coincide with leading series members to the higher limits, contain a large share of the 5p oscillator strength. Analysis of line profiles above and below the first threshold suggests that these resonances may decay with high probability to double ions.