The adsorption of atomic hydrogen on Cu(111) investigated by reflection-absorption infrared spectroscopy, electron energy loss spectroscopy and low energy electron diffraction

Abstract

Hydrogen atoms were adsorbed on Cu(111) at 150 K. The vibrational spectrum of the adsorbed hydrogen was measured by both reflection-absorption infrared spectroscopy (RAIRS) and electron energy loss spectroscopy (EELS) in the temperature range 90–280 K. The saturated surface displayed a (3 × 3) LEED pattern which was converted to a (2 × 2) pattern on heating to 186 K. The vibrational spectrum observed by EELS was little affected by this structural transformation. The major energy loss peak at 1040 cm −1 was assigned to the symmetric stretching mode of hydrogen in a two-fold bridge site. The infrared spectrum revealed more detail, including a second sharp absorption band at 1150–1170 cm −1 which was assigned to the first overtone of the deformation mode of hydrogen in a two-fold bridge site. The intensity of the electron energy loss peak, excited by dipole scattering, and of the infrared absorption bands provided an estimate for the effective charge, e ∗, of the hydrogen adatom of 0.05–0.06 e which is similar to values previously estimated for the hydrogen adatom on W(100).