Intensity Distribution in the Electron-Impact Spectrum of Carbon Monoxide at High-Resolution and Small Scattering Angles

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Abstract
An electron spectrometer, which provides velocity selection before scattering, is described; and the results of a study of relative intensities in the carbon monoxide spectrum are reported. The vibrational levels of the fourth positive band system have been resolved and relative intensities determined for the first nine. The relative intensities are compared with calculated Franck—Condon factors. The agreement is good at low vibrational quantum numbers but noticeable discrepancies are found for high‐vibrational levels. The problem of calculating relative oscillator strengths from a fully resolved spectrum is considered and applied to data obtained in the present research. Relative oscillator strengths are compared with those obtained previously from unresolved spectra. If the Born approximation is valid, then the electron‐impact and ultraviolet absorption spectra should be closely similar. This is actually observed for most of the spectrum but the transition at 12.79 V is an outstanding exception. The relative oscillator strength obtained from the electron‐impact spectrum exceeds that from the ultraviolet absorption spectrum by almost a factor of 3. The reason for this anomaly is not known.

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