Ultraviolet photoelectron spectroscopy analysis of lithium and deuterium interactions with graphite

Lithium wall conditioning has been implemented in fusion devices such as TFTR, CDX-U, FTU, T-11M, TJ-II and NSTX and has yielded improved plasma performance. Offline experiments at Purdue University have investigated the mechanism by which Li interacts with D. X-ray photoelectron spectroscopy (XPS) analysis has shown that deuterium irradiation induces interactions with Li-C and Li-O bonds. Ultraviolet photoelectron spectroscopy (UPS) shows Li$_{2}$O 2p orbital emission energy of 6.5 eV [1]. UPS probes the outermost valence electron orbital (probe depth $\sim $1nm), and yields information more sensitive to chemical bonding than XPS (probe depth $\sim $10nm). This work examines D interaction with lithiated graphite. Additionally, high-resolution electron energy loss spectroscopy (HR-EELS) provides complementary information regarding H bond hybridization.\\[4pt] [1] D. Ensling et al. Applied Surface Science 255 (2008) 2517--2523.