“…Briefly, the instrument consisted of an ion pumped bell jar with a base pressure of approximately 3 · 10 À10 Torr. The W(1 1 0) single crystal could be cooled with liquid nitrogen to 90 K and resistively heated to >2000 K, with the temperature monitored by measuring the resistance of the sample [14]. A Mg Ka X-ray source and a helium discharge were available for XPS and UPS, respectively.…”