Nuclear Magnetic Resonance Studies of Chemisorption of Alkali-Metal Atoms on a W(110) Surface

NMR measurements were performed with nuclear-spin—polarized alkali-metal atoms (${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$) adsorbed on a clean and an oxygen-covered W(110) surface. For the desorbed alkali-metal ions the change of polarization due to the radio-frequency field was detected by beam-foil spectroscopy. Energy splittings of the nuclear states were found arising from the interaction of nuclear quadrupole moments with electric field gradients. They reflect the spatial charge distribution in the vicinity of the adsorbed alkali-metal atoms.