Velocity and electronic state distributions of sputtered Fe atoms by laserinduced fluorescence spectroscopy J. Vac. Sci. Technol. A 2, 693 (1984); 10.1116/1.572430High resolution continuous wave laser induced fluorescence spectroscopy of sputtered Zr atoms Doppler shift laser induced fluorescence spectroscopy was used to determine the relative sputtering yields and number density velocity distribution of sputtered neutral ground state zirconium atoms. Neither change in primary ion energy over the range 1-3 keY nor change in primary ion mass (Ar+, Kr+) affected the velocity distribution despite large changes in the sputtering yield. The measured number density velocity distributions n Iv) are well explained by standard linear collision cascade theory and follow the expressionwhere Vb is the velocity corresponding to a surface binding energy, Eb = 1/2m z,u;, with Eb = 6.305 eV, the bulk zirconium sublimation energy. Surprisingly, the number density velocity distributions of zirconium atoms sputtered in two excited states (a 3 F 3.4) are indistinquishable from that measured for ground state zirconium atoms. Further, the sputtering yield dependence on primary ion energy for the 3F 3 ,4 was also, within experimental error, the same as for the lF, ground state zirconium. The sputtering yield for the two excited states represents almot 40% of the total yield of zirconium. Evaluation of the results incorporates for the first time the effects of power broadening, transit time broadening, and velocity dependent fluorescent detection efficiencies.6448

The use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of 235U/238U ratios by resonance ionization mass spectrometry (RIMS) to decrease laser-induced isotopic fractionation. By broadening the bandwidth of the first laser in a three-color, three-photon ionization process from a bandwidth of 1.8 GHz to about 10 GHz, the variation in sequential relative isotope abundance measurements decreased from 10% to less than 0.5%. This procedure was demonstrated for the direct interrogation of uranium oxide targets with essentially no sample preparation.

Surface-enhanced Raman scattering (SERS) of partially protonated poly(2-vinylpyridine) (P2VPy) adsorbed onto an electrochemically roughened silver electrode is reported as a function of applied potential. The species on the electrode surface is predominantly pyridinium ion when the electrode potential is positive of the point of zero charge (EJ and predominantly neutral pyridine near Ez. Orientation effects involving the polymer chain are visible in the fingerprint region of these spectra. The species vs potential dependence is different for the polymer compared with low molecular weight probe molecules of pyridine and 2methylpyridine. The presence of the polymer substantially improves the stability of the active sites responsible for SERS activity to cathodic excursions to Ez in chloride electrolyte. The differences observed with the polymer are explained on the basis of its lower solubility and the "anchoring" of positive charges within the double-layer region.

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