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

Thermal desorption mass spectrometry (TDMS), UV photoelectron spectroscopy (UPS), low-energy electron diffraction (LEED), and contact potential difference measurements have been employed to study the interaction of cyclopropane with the reconstructed Ir (110)–(1×2) surface. At an adsorption temperature of 100 K cyclopropane dissociates on the surface with a reaction probability of 0.87±0.1. This overlayer saturates at a coverage of cyclopropane of (2.1±0.2)×1014 cm−2. Upon further exposure, cyclopropane adsorbs molecularly into two different adsorption sites up to a saturation coverage of 6.6×1014 cm−2. The parameters of the desorption rate coefficients based upon Arrhenius constructions for low coverages of the two desorption states are Ed = 6.4±1 kcal mol−1 and νd = 1.0×109±1 s−1, Ed = 8.3±1 kcal mol−1 and νd = 4.5×1010±2 s−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.