Negative ion mass spectra of acrylonitrile were measured for the electron energies of 80, 40 and 9.5 eV. Emphasis was laid on the abundance of the negative ions relative to the positive ions measured for the energies of 80, 40 and 15 eV, respectively. The ionization efficiency (IE) curves were also determined up to 25 eV for the ions of m⁄e 25(C2H−), 26(CN−), 27(HCN−), 38(C2N−), 39(CHCN−), 40(CH2CN−) and 50(C3N−). The electron impact of 80 eV and 40 eV gave almost the same distribution of m⁄e for negative ion mass spectra. Besides the most intense peak of CN− ions, relatively strong peaks of C3N−, C2H−, C2− and C2N− ions were observed. In 9.5 eV, CN− ions predominated over other ions. Yields of the ions showed a good linearity against the pressure in the range used for usual chemical analysis, irrespective of electron energy. Comparison of the yield of CN− ions with that of C2H3CN+ gave the values 1.2×104 and 1.9×104 for C2H3CN+/CN− at 80 eV and 40 eV, respectively, and 47.6 at 9.5 eV (15 eV for the positive ions). The plausible reaction schemes expected to occur at each onset observed in the IE curves were also sought thermochemically by using ΔHf values of the reactant and products. A value \gtrsim2 eV was obtained for the electron affinity of C2H.

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 studies of this series were extended to the negative ions of m⁄e 26 and 42 obtained from nitroalkanes; nitromethane, nitroethane, 1-nitropropane, and 2-nitropropane. For m⁄e 26 (probably, CN−) ions, the contribution of three or two processes in the range from zero to ∼20 eV of electron energy was observed for nitromethane or other samples. On the basis of ΔHf values of the reactants and products, and of the value of EA(CN), the plausible reactions to be assigned to each process were presented. For the first process, CH3NO2+e−→CN−+H2O+OH, RNO2+e−→CN−+R1OH+OH. For the second process, CH3NO2+e−→CN−+H2O+O+H, CH3NO2+e−→CN−+H2+O2+H, RNO2+e−→CN−+R1+HO2+H, and C3H7NO2+e→CN−+C2H4+H2+O+OH irrespective of kind of nitropropane. For the third process, CH3NO2+e−→CN−+3H+O2. For m⁄e 42 (probably, CNO−) ions, the contribution of two processes was observed. By taking ΔHf (CNO)=x (eV), EA(CNO)=y (eV), and also combining the observed onset values with the calculated values of appearance potential of reactions to be assigned for each process — for the first process, CH3NO2+e→CNO−+H2+OH, RNO2+e−→CNO−+R1OH+H; for the second process, CH3NO2+e−→CNO−+HO+2H, CH3NO2+e−→CNO−+H2+O+H, RNO2+e−→CNO−+R1O+2H– a relation of x−y\simeq2(eV) was derived.

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The ionization efficiency (IE) curves of NO2−, O− and CH2NO2− ions from nitroalkanes (nitro-methane, nitroethane, 1-nitropropane and 2-nitropropane) have been measured with a Hitachi RMU-6D mass spectrometer. Based on each authorized value of IP(CH3, C2H5, C3H7, O and H), D(C–NO2, C–H, C–C, NO–O and N–O), EA(NO2 and O) and the excitation energy of CH3, the respective onsets observed for the electron energies above ∼3 eV on the IE curves were suggested to be interpreted as appearance potentials of the following reactions. For NO2− ions, RNO2+e→R*+NO2−, RNO2+e→R+NO2−+e; for O− ions, RNO2+e→RNO+O−, RNO2+e→RN+O+O−, RNO2+e→RN++O+O−+e;for CH2NO2− ions, CH3NO2+e→H+ CH2NO2−+e, RNO2+e→H+R1+CH2NO2−. On the other hand, the strong peak of NO2− ions due to the dissociative electron capture process (RNO2+e→R+NO2−) was observed at the lower electoron energy. Furthermore, a value of EA(CH2NO2) was presented to be ∼0.5 eV.