Chemisorption and reaction of cyclopropane on the (110) surface of iridium

摘要

Thermal desorption mass spectrometry (TDMS), UV photoelectron spectroscopy (UPS), lowhyphen;energy electron diffraction (LEED), and contact potential difference measurements have been employed to study the interaction of cyclopropane with the reconstructed Ir (110)ndash;(1times;2) surface. At an adsorption temperature of 100 K cyclopropane dissociates on the surface with a reaction probability of 0.87plusmn;0.1. This overlayer saturates at a coverage of cyclopropane of (2.1plusmn;0.2)times;1014cmminus;2. Upon further exposure, cyclopropane adsorbs molecularly into two different adsorption sites up to a saturation coverage of 6.6times;1014cmminus;2. The parameters of the desorption rate coefficients based upon Arrhenius constructions for low coverages of the two desorption states areEd= 6.4plusmn;1 kcalthinsp;molminus;1and ngr;d= 1.0times;109plusmn;1sminus;1,Ed= 8.3plusmn;1 kcalthinsp;molminus;1and ngr;d= 4.5times;1010plusmn;2sminus;1. The work function decreases by 0.5 eV during formation of the dissociated hydrocarbon residue at 100 K and decreases further (a total decrease of 0.7 eV) during the adsorption of molecular cyclopropane.