Surface diffusion and desorption kinetics for perfluorohyphen;nhyphen;butane on Ru(001)

摘要

The surface diffusion and desorption kinetics for perfluorohyphen;nhyphen;butane on Ru(001) were examined using laserhyphen;induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. The surface diffusion displayed Arrhenius behavior and was coverage independent. The surface diffusion parameters for perfluorohyphen;nhyphen;butane on Ru(001) wereEdif=2.9plusmn;0.3 kcal/mol andD0=5.9times;10minus;2plusmn;0.2cm2/s. The desorption parameters for perfluorohyphen;nhyphen;butane on Ru(001) wereEdes=13.8plusmn;0.6 kcal/mol and ngr;des=2.8times;1021plusmn;0.1sminus;1. In comparison, the surface diffusion parameters fornhyphen;butane on Ru(001) wereEdif=3.5plusmn;0.2 kcal/mol andD0=1.4times;10minus;1plusmn;0.2cm2/s. The desorption parameters fornhyphen;butane on Ru(001) wereEdes=11.9plusmn;0.5 kcal/mol and ngr;des=3.6times;1015plusmn;0.1sminus;1. The corrugation ratio, defined as OHgr;equiv;Edif/Edes, was determined to be OHgr;=0.21 for perfluorohyphen;nhyphen;butane on Ru(001). This corrugation ratio was substantially different than the corrugation ratio of OHgr;ape;0.30 measured fornhyphen;butane and various othernhyphen;alkanes, cycloalkanes and branched alkanes on Ru(001). The comparison between perfluorohyphen;nhyphen;butane and the other alkanes indicates that fluorination lowers the surface corrugation ratio on Ru(001). Likewise, fluorination significantly increases the preexponential for desorption from Ru(001). This study illustrates the magnitude of substituent effects on surface diffusion and desorption kinetics for a physisorbed molecule on a singlehyphen;crystal metal surface.