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Slow highly charged ions approaching surfaces at very close distances (∼nm) are known to capture many electrons in highly excited states forming hollow atoms(1)(2). These hollow atoms quickly decay to their ground states through a long cascade of autoionization processes( Auger transitions) which may be balanced , as these ions are still close to the surface, by a series of electron captures. This actual sequence of many events of capture and autoionization, alternate or not, is not experimentally known to date, and depends on the charge of the ions and of the capture processes which may be very different above metals and insulators. We review in this paper two new experiments on the kinematics of fully decelerated highly charged ions(Ar18+) above dielectric and metal surfaces, and on the behavior of ions of lower charge states (O7+ and Ne9+) above the same surfaces. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Fluorescence-detected x-ray absorption spectroscopy probes the fine structure of electronic energy levels with sub-eV resolution by scanning a monochromatic synchrotron beam through the corresponding absorption edge and measuring the intensity of the resulting x-ray fluorescence. For dilute samples, grating spectrometers lack the detection efficiency and conventional Si(Li) or Ge detectors often lack the energy resolution to separate the weak fluorescence signal from strong nearby emission lines. We have built a high-resolution, highefficiency cryogenic detector system for synchrotron-based soft x-ray spectroscopy. The sensor is a 3 x 3 array of 200 µm x 200 µm superconducting Nb-A1-A1Ox-A1-Nb tunnel junctions with an energy resolution of ≈15 eV below 1 keV and a total count rate capability of ≈100,000 counts/second. This sensor array is cooled to below 0.4K by a two-stage adiabatic demagnetization refrigerator while held at the end of a 40-cm-long cold finger that can be inserted into a UHV sample chamber for x-ray fluorescence measurements. We present absorption spectra of dilute compounds (≈ 1000 ppm) and will discuss spectrometer performance with respect to the analysis of metalloproteins. [ABSTRACT FROM AUTHOR]

We have conducted low energy X-ray spectroscopy of ion/surface interactions with superconducting tunnel junction (STJ) detectors. The STJ detectors (Nb-Al-AlOx-Al-Nb) developed at the Lawrence Livermore National Laboratory have a high energy resolution and a high count-rate capability. The detectors are operated in an adiabatic demagnetization refrigerator with 60 mK base temperature at the end of a 40 cm long cold finger, which can be inserted into a UHV sample chamber connected to an ion source. We have studied the . interaction of Ar[sup +], O[sup 7+], N[sup 6+] and C[sup 5+] with various targets (Au, SiH and SiO[sub 2]) at a kinetic energy of 10 keV/q. The resolution of 12-15 eV below 1 keV allows the different satellite lines emitted by these ions to be separated. [ABSTRACT FROM AUTHOR]