Structure and dynamics of dense monolayers of NO adsorbed on Rh(111) in equilibrium with the gas phase in the Torr pressure range

Using scanning tunneling microscopy, we show the phase transition between n ew structures of NO on Rh(lll) in equilibrium with the gas phase near 300 K , in the Torr pressure range. Two phases with (2 X 2) and (3 X 3) periodici ty transform into each other as the pressure and temperature change around the equilibrium P-T line. By measuring P and T at coexistence, we determine d the heat of adsorption in the (3 x 3) structure. From the phase boundary dynamics, the activation energy barrier between phases were estimated. The results demonstrate that unique information can be obtained from high-press ure and high-temperature studies.