Adsorption of CO on a Pt{110} (1 x 2) surface pre-cooled to 160K was found to proceed without loss of the (1 x 2) reconstruction, in contrast to adsorption at higher temperatures. Using high resolution electron energy loss spectroscopy, It was found that adsorption occurred initially into a linear species, with the additional occupation of bridged sites at fractional coverages above 0.2. At saturation, the ratio of bridged to linear species was 1:3. The absorption intensity from the linear species was shown to be 2.5 times that of the bridged species. Heating the saturated surface to temperatures between 280 and 340K results in an irreversible transformation of the bridged species to linear, and a lifting of the (1 x 2) reconstruction to (1 x 1). The orientation of CO molecules in the low temperature metastable phase on the (1 x 2) surface was determined using angle-resolved photoemission, with electron collection in the plane orthogonal to the incidence plane. The CO molecules were found to be tilted away from the macroscopic surface normal, along the [100] azimuth, by 15°. This contrasts with previous findings for the stable phase of CO on the annealed (1 x 1) surface, where the tilt angle was found to be 26° along the [211] azimuth.

Characterisation of a Low Temperature Surface Phase of CO on Pt{110}. P.Hofmann, S.R.Bare, D.A.King: Physica Scripta, 1983, T4, 118-21