Dissociative-electron-attachment cross sections for the production of OH-, 0-, and H-from water vapor have been determined. These cross sections are discussed within the framework of resonance scattering theory. The relatively low cross sections for the production of OH-, 1.2,0.85, and 0.85X 1()-21 cm 2 molecule-1 for maxima of 6.4,8.4, and 11.2 eV, suggest that the atoms in the H20-complex are loosely. bound together and behave as essentially independent entities. All of the negative ions from H20 appear to be produced from three different electronic states of the molecule. Results from this study are used to draw a hypothetical potential energy diagram for H20.

The retarding potential difference method has been used to measure ionization efficiency curves of CHaX+ (X=H, F, Cl, Br, I), CHa+, and X+ from methane and the methyl halides in a time-of-flight mass spectrometer. Discontinuities between linear segments of the ionization efficiency curves are interpreted as appearance potentials (A.P.) of electronic states or processes. For all CHa+, A.P.'s occur at 1.1, 1.7,2.7, and about 3.4 eV above onset in the ion pair region. Empirical knowledge of this structure makes it possible to identify the A.P. for the ion-neutral pair, CHaLX, in their ground states. Combining these data and the A.P.'s for X+/CHaX gives the ionization potential for CHa and the bond dissociation energies, D(CHa-X).

The complete negative ion mass spectra and relative sensitivity for positive and negative ion formation in various organic compounds are herein reported for the first time. These compounds include methane, the C2— hydrocarbons, n-butane, and all of the alkyl alcohols through the butyls. A limited comparison of the observed ionic patterns with molecular structure and chemical properties manifests a correlation. Relative sensitivities for positive and negative ion formation in these compounds show that formation of positive ions is about four orders of magnitude more probable than formation of negative ions under the conditions used in this study.

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The abundances of, and the total and individual cross sections for, primary products (positive ions, neutral species, and negative ions) resulting from elementary reactions induced by the absorption of energy by CH4 from ionizing radiation (100-eV electrons) have been measured. This was accomplished with the dual electron beam section of our wide-range radiolysis source. The results show that positive ions and free radicals are produced in nearly equal abundances, 45% and 55%, respectively. On the other hand, negative ions are less abundant by about four orders of magnitude. The total cross section for positive ionization (σI) by 100-eV electrons is 3.8×10−16 cm2 and that for the formation of neutral species (σN) is 4.7×10−16 cm2. To independently test the reliability of the dual electron-beam ion source, the total and individual cross sections for ionization of Ar by 100-eV electrons were measured for comparison with published values. Our value for the total cross section (σI) of 3.24× 10−16 cm2 is in satisfactory agreement with those reported by other workers, whose values range from (2.8 to 3.6)×10−16 cm2.