Hydrogen phonon spectra on PT(111) at T = 100K and T = 160K.

Infrared reflection absorption spectroscopy (IRRAS) has been used to identify the hydrogen phonon absorption with strict dipole character for the system Pt(111)-(1X1)H over the 800- 4000 cm sup (-1) frequency region. A single hydrogen vibrational feature was observed at ~ above nu=1254 cm sup (-1), possessing a FWHM=90(10) cm sup (-1) and an e /e=0.019(2). The likely origin of this feature is the symmetric stretching mode (nu sub 1) of hydrogen chemisorbed in a three fold fcc site, but ambiguity in this assignment persists when additional EELS vibrational data is considered.