The electron impact excitation cross section for the X 1Σ+g→ a 1Πg transition in N2 has been measured from 13 to 100 eV by an inelastic electron scattering technique. The cross section varies from a maximum value of 3.6×10−17 cm2 between 15 and 18 eV to 5.2×10−18 cm2 at 100 eV. The incident electron impact energy was calibrated by an optical technique. The agreement between the measured intensities of the v′=0–6 vibrational bands of the transition and the intensities predicted by the Franck–Condon factors was found to be within experimental error. The cross section results of the present experiment are in excellent agreement with those of previous investigators obtained with a variety of techniques up to 30 eV. At the higher energies, the present values agree within experimental error with the results of Holland at 100 eV and those of Aarts between 60 and 100 eV.

Dissociative excitation of CO by electron impact: Translational spectroscopy of longlived highRydberg fragment atoms J. Chem. Phys. 60, 1358 (1974); 10.1063/1.1681205 Dissociative excitation of N2 by electron impact: Translational spectroscopy of longlived highRydberg fragment atomsThe production of hydrogen and carbon atoms in metastable and high-lying Rydberg states due to electronimpact dissociation of CH. and CD. has been investigated for incident electron energies from threshold to 300 eV. Onset energies for the production of metastable hydrogen atoms were observed at electron impact energies of 22.0±O.5, 25.5±O.6, 36.7±O.6, and 66±3 eV, and at 26.6±O.6 eV for the production of metastable carbon atoms. Most of the excited H fragments appear to have been formed initially in highlying Rydberg states with the metastable H(2 S) state populated principally by cascade. The differential cross section, (dCTldOho" for the dissociative excitation of H atoms to metastable and high-lying Rydberg states reached a maximum value of approximately I X 10-19 cm'lsr at 100 eV. At the same energy, the metastable carbon differential cross section is 2 X 10-'0 cm'/sr.

The relative emission cross section for the N2 second positive system (0, 0) and (1, 0) bands excited by electron impact has been measured for incident electron energies from threshold to 17 eV. By using a high energy-resolution electron spectrometer coupled to an optical detection system, it was possible to perform the measurements with an incident electron beam having an energy half width of 50 meV (FWHM). Observation of various scattering resonances in nitrogen and helium provided an accurate calibration of the incident electron energy. The maximum of the N2 second positive system (0, 0) band emission cross section (λ3371 Å) was found to be at 14.02 ± 0.05 eV. The maximum for the (1, 0) second positive band (λ3159 Å) was found to be at 14.3 ± 0.1 eV. Two small structural features corresponding to the onset of additional channels for population of the N2 C 3IIu state were observed at 11.48 eV and between 11.8 and 12.3 eV. The first feature was pressure independent and appeared only in the (0, 0) band emission cross section. This feature apparently arises as a consequence of decay of the compound state responsible for the 11.48 eV N2 elastic scattering resonance to the N2 C 3Πu(v′=0) state. The second feature was broad and pressure dependent. It appeared more strongly in the (1, 0) band cross section than in that for the (0, 0) band. Collisional quenching of the N2 E 3Σg+ state via a collision-induced crossing into the vibrational states of the N2 C 3IIu state appears to be the best explanation of this effect.

The cross section for elastic scattering of electrons from N2 has been measured between 13 and 100 eV. The relative differential cross sections for elastic scattering and for excitation of the C 3Il. v' = 0 and I bands were measured over the angular range from 20· to 90· in the 13-35 eV region and from 5· to 90· in the 40-100 eV region. The integrated cross sections were placed on an absolute basis by normalizing the C 3Il. v' = 0 excitation cross section to the known emission cross section for the Second Positive system of nitrogen (C 3Il. -> B 3Il g ) and by calibrating the electron spectrometer with respect to other electron scattering results. The total elastic scattering cross section varies from 12.3 X 10-16 cm 2 (±50%) at 13 eV to 3.9X 10-16 cm 2 (±50%) at 100 eV.The pressure dependence of the scattered signal was studied to demonstrate the absence of multiple scattering. Analysis of the data up to pressures of 25 mtorr by the method of Lassettre and Francis 19 demonstrated the lack of multiple scattering in the elastic and inelastic C 3ITu channels. The ratio of elastic/C 3ITu signal was independent of pressure over the same pressure range. During the actual experiments, the pressure of the

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