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 new structures of NO on Rh(111) in equilibrium with the gas phase near 300K, in the Torr pressure range. Two phases with (2x2)and (3x3) periodicity transform into each other as the pressure and temperature change around the equilibrium P-T line. By measuring P and T at coexistence, we determined the heat of adsorption in the(3x3) structure. From the phase boundary dynamics, the activation energy barrier between phases was estimated. The results demonstrate that unique information can be obtained from high-pressure and high-temperature studies.