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Ta(110) Surface And Subsurface Core-Level Shifts And 4f7/2 Lineshapes, D. Mark Riffe, G. K. Wertheim

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High-resolution 4f core-level spectra of the Ta(110) surface region have been obtained at 80 and 300 K with 70- and 100-eV synchrotron radiation. The data show that the subsurface core-level binding-energy shift (compared to deeper-lying atoms) for a close-packed bcc(110) surface can be substantial: 65±15 meV for the first underlayer atoms of Ta(110). The surface core-level shift is 360±12 meV at 80 K and decreases by 13±2 meV at 300 K. Final-state screening in both the bulk and surface layers is well described by a constant singularity index of 0.133±0.012. An enhanced phonon broadening at the surface corresponds to a …