Knowledge Bank

The vibrational spectra of molecules adsorbed on metal surfaces usually are measured with electron energy loss $spectroscopy1$. In recent years there has been a renewal of interest in measuring these spectra with infrared $absorption2$ and Raman $scattering3$. We present apparatus for making these measurements, and report the infrared and Raman spectra of acetone and of CO adsorbed on low Miller index planes of nickel crystals. The samples are cleaned by thermal desorption and ion bombardment in an ultrahigh vacuum monitored by a residual gas analyzer. Spectra are compared from samples at room temperature and at liquid nitrogen temperature. The polarization dependence of the spectra will be discussed.