Reflection-absorption infrared spectrum of α-CO chemisorbed on polycrystalline tungsten

The infrared spectrum of chemisorbed α-CO on polycrystalline tungsten has been studied using ultrahigh vacuum techniques. The α-CO state has been spectroscopically resolved into two states, designated α 1-CO (wavenumber ∼2128 cm −1) and α 2-CO (wavenumber ∼2090 cm −1). α 2-CO adsorbs predominantly in the first stages of α-CO adsorption; α 1-CO forms primarily at high α-CO coverages at the partial expense of α 2-CO. α 1-CO is found to desorb at a slightly lower temperature than α 2-CO. Both α-CO states are postulated to involve sp-hybridized carbon which is bonded to the tungsten surface. These states have previously been detected in electron impact desorption measurements, where α 1-CO was shown to liberate CO + and α 2-CO to liberate O +.