Bridging the Pressure Gap in Surface Science at the Atomic Level: H / Cu ( 110 )

The structural response of the Cu(110) surface to ${\mathrm{H}}_{2}$ gas pressures ranging from ${10}^{\ensuremath{-}13}$ to 1 bar is studied using a novel high-pressure scanning tunneling microscope (HP-STM). We find that at ${\mathrm{H}}_{2}$ pressures larger than 2 mbar the Cu(110) surface reconstructs into the ( $1\ifmmode\times\else\texttimes\fi{}2$) ``missing-row'' structure. From a quantitative analysis of the pressure dependence of the surface reconstruction, we conclude that Cu(110) responds identically to hydrogen at ultrahigh vacuum conditions and at atmospheric pressures. From the HP-STM data, we extract refined values for the adsorption and desorption rate constants.