Berlin 2001 – wissenschaftliches Programm
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A: Atomphysik
A 6: Spectroscopy
A 6.1: Vortrag
Dienstag, 3. April 2001, 15:45–16:00, H1028
Isotope shift, hyperfine structure and J-determination of narrow autoionizing states in gadolinium — •Klaus Blaum1, Bruce A. Bushaw2, Wilfried Nörtershäuser2, and Klaus Wendt1 — 1Institut für Physik, Universität Mainz, D-55099 Mainz, Germany — 2Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352, USA
Triple-resonance excitation to autoionizing states above the first ionization limit of Gd has been studied with high-resolution cw-lasers. Experimentally determined line widths range from a few cm−1 down to 10 MHz and correspond to autoionization lifetimes from ps to greater than 15 ns. The upper value is, to our knowledge, one of the longest lifetimes ever observed for an autoionizing state. The cross section of some of these transitions is more than 5 orders of magnitude greater than for ionization into the nearby continuum. This permits highly efficient ionization even when using low power cw-lasers, which has profound implications for ultrasensitive analytical applications. Modest saturation of the ionization step has been observed using a cw-diode-laser. Isotope shifts and hyperfine structure have been measured for a number of the narrower autoionizing states. By comparing spectra derived from excitation schemes that use different J angular momentum values in the intermediate states, we have determined the J value, with J = 3−7, for more than 300 even-parity autoionizing states occuring within the first 90 cm−1 above the ionization limit. These data should lead to a better understanding of the rich continuum structure of elements with multiple open subshells.