The adsorption of benzene on Si(111)-7×7 has been studied using high-resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). Both chemisorbed and physisorbed benzene were observed at an adsorption temperature of 110 K. Chemisorbed benzene desorbs molecularly at 350 and 364 K while physisorbed molecules desorb at 180 K. In the HREELS studies, two separate energy losses at 2920 and 3025 cm -1 were observed for chemisorbed benzene, attributable to the C-H stretching vibrations of sp 3 and sp 2 carbon atoms, respectively. In addition, the formation of Si-C bond is also evidenced at a vibrational frequency of 540 cm -1 . Our results clearly demonstrate that benzene is di-σ bonded to the adjacent adatom and rest atom on Si(111)-7×7, forming a 1,4-cyclohexadiene-like structure.

The surface chemistry of furan adsorbed on Ru(001) at 80 K has been explored using thermal desorption spectroscopy, x-ray and ultraviolet photoelectron spectroscopies and high resolution electron energy loss spectroscopy (HREELS). Furan adsorption follows a three-dimensional island growth mode. Three desorption peaks, corresponding to multilayer, second layer, and monolayer were identified at 117, 142 and 220 K, respectively. Monolayer species strongly bind to the surface, showing a much lower O(1s) binding energy (532.9 eV) as compared to the physisorbed furan (534.8 eV). HREELS reveals that within the monolayer, there are two different chemisorbed species with molecular rings oriented either tilted or parallel to the surface. By annealing the surface to 180 K, the parallel furan π complex undergoes α-C electrophilic addition and H elimination, forming the tilted α-furyl species and Ru–H. The α-furyl can either recombine with hydrogen to form furan desorbing between 180 and 250 K, or decompose to give adsorbed oxygen atoms and a metallocyclelike intermediate through a direct oxygen abstraction mechanism. Further thermal annealing leads to the formation of carbon monoxide and hydrogen desorbing from the surface.

UV photoelectron spectroscopy was used to investigate the electronic structure of 10 very strong, neutral amine bases of guanidine and phosphazene type. The spectral assignment was based on the band intensities, HeI/HeII band intensity changes (when available), comparison with the spectra of related compounds and MO calculations. The relative importance of various factors influencing basicity is discussed.

The adsorption and dissociation of H2S on GaAs(100) has been studied using high-resolution electron energy loss spectroscopy, thermal desorption spectroscopy, and isotope exchange techniques. The dissociative adsorption of H2S at 100 K produces only H–As species with a vibrational frequency of 2072 cm−1. Upon warming to 200 K, the vibration of H–As clearly shifts to 2105 cm−1, corresponding to a free H–As species. In addition, the formation of H–Ga (1887 cm−1) is also observed upon thermal annealing. In coadsorption studies of H2S and D atoms, three main desorption features of H2S were observed at 135, 200, and 375 K, respectively. The peaks at 135 and 375 K can be attributed to the desorption of molecularly adsorbed H2S and the recombinative desorption of adsorbed H and HS, respectively. In addition to the 375 K peak, the desorption feature at 200 K also undergoes isotope exchange between coadsorbed D atoms and H2S. These observations strongly suggest that the dissociative adsorption of H2S on GaAs(100) involves an intermediate of Ga–HS—H–As.