Surface infrared reflection-absorption spectroscopy using a tunable diode laser

Single-reflection infrared reflection-absorption spectra (IRRAS) of adsorbates on surfaces have been obtained using a tunable diode laser radiation source. Surface sensitivity is achieved through the use of polarization modulation, and the high brightness of the laser light source has made possible the observation of vibrational modes at energies much lower than those accessible with conventional blackbody sources. Results are presented for the chemisorption of oxygen on polycrystalline aluminum showing surface (580/cm) and subsurface (890/cm) Al-O stretching modes at sub-monolayer coverage.