Calculations of long-range potential wells for highly excited homonuclear and heteronuclear alkali dimers Erratum: Measurements of the electric dipole polarizabilities of the alkali halide dimers [J. Chem. Phys. 8 0, 3580 (1984)] J. Chem. Phys. 81, 2189 (1984); 10.1063/1.448196 Measurements of the electric dipole polarizabilities of the alkali halide dimers
We report measurements of absolute cross sections for the electron-impact ionization and dissociative ionization of the deuterated methane molecule and the (x = 1 - 3) free radicals from threshold to 200 eV using the fast-neutral beam technique. We used the deuterated rather than the protonated target species to facilitate a better separation of the various product ions from a given parent molecule in our apparatus. Good agreement was found between our results and the most recent measurements in . Our results for and agree well with earlier measurements carried out under different experimental conditions. The present results for the CD free radical are the first ionization cross section measurements for this target. A common feature of all four targets studied in this work was a dominant parent ionization cross section with essentially the same absolute value of 1.6 - at 70 eV. A comparison of the experimentally determined total single ionization cross sections with calculated cross sections using a modified additivity rule showed very good agreement for all four targets.
We report measurements of the absolute cross sections for the electron-impact ionization of SO2 from threshold to 200 eV. Absolute cross sections for the formation of the SO+2 parent ions and of the SO+, S+, O+, and O+2 fragment ions were obtained independently in two different laboratories using two different experimental techniques with uncertainties ranging from ±18% to ±25%. The level of agreement between the absolute cross sections (at 70 eV) obtained by the two techniques ranges from about 10% for SO+2 and SO+ to 20% for (S++O+2) and O+, which in all cases is well within the combined error margins of the two measurements. The high resolution capability of the mass spectrometer employed in one experiment enabled the separation of the S+ and O+2 fragment ions, which are separated by only 0.017 76 atomic mass units (amu), for the first time. The single positive ion formation is the dominant process for all observed product ions. The total single SO2 ionization cross section obtained by the two techniques agreed to within 8%. A comparison of the experimentally determined total SO2 single ionization cross sections with calculated cross sections based on a modified additivity rule revealed agreement to within 20%.
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