New experimental temperature programmed desorption (TPD) data have been obtained under carefully controlled conditions for atomic deuterium on the single crystal Si(100)-2×1 surface. A wide range of coverages from Θ=1.5 to 0.05 ML was used. A kinetic lattice-gas model has been developed which describes atomic hydrogen (or deuterium) adsorbed on the Si(100)-2×1 surface in terms of four basic units: dihydride (SiH2), doubly occupied dimers (H–Si–Si–H), singly occupied dimers (Si–SiH), and unoccupied dimers (Si=Si). The equilibria between these species have been determined by considering both the lattice partition functions and the vibrational partition functions associated with the Si–H bonds. By using a quasiequilibrium approximation and two competing desorption routes corresponding to formation of the β1 and β2 peaks, the TPD spectra for hydrogen (deuterium) molecules are determined and compared with the new experimental data. Fitting the experimental curves with the simulated data from the aforementioned model showed that the desorption process which leads to the β1 peak obeys first-order kinetics with an A factor of 2×1015 s−1 and activation energy of 57 kcal mole−1, whereas the process giving the β2 peak follows second-order kinetics with an activation energy of 47 kcal mole−1 and an A factor (expressed in 1st order units) of 3×1015 s−1.

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He I and He I1 spectra are reported for the isoelectronic molecules CF2 and 03. New values are reported for the first and higher ionization potentials. The spectra are interpreted with the aid of semi-empirical molecular orbital calculations.

A complete analysis has been made for each of the high-resolution proton magnetic resonance spectra of naphthalene, anthracene, pyrene, perylene, triphenylene, and coronene at infinite dilution in CS2 or CCl4. A partial analysis has been made for phenanthrene. The analyses yield absolute values for the chemical shifts and spin coupling constants. A correlation has been made between the π-bond order of the particular (C–C) bond and the spin coupling constant. Theoretical values for the ``ring current shifts'' were obtained using London type molecular orbital calculations. The agreement between experimental and theoretical values is satisfactory in that the relative positions of the proton shifts are correctly predicted in all cases.

The He1 vacuum ultraviolet photoelectron spectrum of the methyl radical produced by pyrolysis of azomethane has been investigated. Three ionization potentials, corresponding to the for!m!ion of the ' A ; , 3E' and 'E' ionic states, have been observed with vertical ionization potentials of 9.54, 14.76 and 16.10eV respectively. The observed band positions have been interpreted with tb: aid of both ab initio and semiempirical molecular orbital calculations.The band associated with the first ionization potential is the only one for which \ibrational structure could be rcsolved. This has been investigated in both CH3 and CD3 using He1 and Ye1 radiation. From the Franck-Condon envelope of this band and the observed shifts on deatcration, it is concluded that the methyl radical is essentially planar in its ground electronic state. The hctors which control the values of the out-of-plane deformatim frequencies in the ground state of CH, and CH; are discussed in detail. Jahn-Teller splitting has been detected in the band arsminted with the sxond ionization potential of CH,.