Vibrational excitation of D2 by low energy electrons

Excitation coefficients for the production of vibrationally exicted D2 by low energy electrons have been determined from measurements of the intensity of infrared emission from mixtures of D2 and small concentrations of CO2 or CO. The measurements were made using the electron drift tube technique an...

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Veröffentlicht in:The Journal of chemical physics 1985-06, Vol.82 (11), p.4999-5011
Hauptverfasser: BUCKMAN, S. J, PHELPS, A. V
Format: Artikel
Sprache:eng
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Zusammenfassung:Excitation coefficients for the production of vibrationally exicted D2 by low energy electrons have been determined from measurements of the intensity of infrared emission from mixtures of D2 and small concentrations of CO2 or CO. The measurements were made using the electron drift tube technique and covered electric field to gas density ratios (E/n) from (5 to 80)×10−21 V m2, corresponding to mean electron energies between 0.45 and 4.5 eV. The CO2 and CO concentrations were chosen to allow efficient excitation transfer from the D2 to the carbon containing molecule, but to minimize direct excitation of the CO2 or CO. The measured infrared intensities were normalized to predicted values for N2–CO2 and N2–CO mixtures at E/n where the efficiency of vibrational excitation is known to be very close to 100%. The experimental excitation coefficients are in satisfactory agreement with predictions based on electron–D2 cross sections at mean electron energies below 1 eV, but are about 50% too high at mean energies above about 2 eV. Application of the technique to H2 did not yield useful vibrational excitation coefficients. The effective coefficients in H2–CO2 mixtures were a factor of about 3 times the predicted values. For our H2–CO mixtures the excitation of CO via excitation transfer from H2 is small compared to direct electron excitation of CO molecules. Published experiments and theories on electron–H2 and electron–D2 collisions are reviewed to obtain the cross sections used in the predictions.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.448673