Absolute Generalized Oscillator Strengths for Four Electronic Transitions in Carbon Monoxide

Abstract

Generalized oscillator strengths have been measured for the $\text{υ′\hspace{0.17em}=\hspace{0.17em}2}$ level of the fourth positive bands of carbon monoxide by comparing inelastically and elastically scattered electrons at 300‐, 400‐, and 500‐eV kinetic energy and using the elastic collision cross sections measured by Bromberg [J. Chem. Phys. 52, 1243 (1970)]. Extrapolation to zero momentum change gives $f_0\text{\hspace{0.17em}=\hspace{0.17em}0.0429}$ . From relative intensity measurements, the limiting oscillator strengths of the levels from $\text{υ′\hspace{0.17em}=\hspace{0.17em}0–12}$ have also been determined. From zero angle spectra, the limiting oscillator strengths for transitions to the $B^1{\Sigma }^{+}{\mathrm{,\; C}}^1{\Sigma }^{+}$ , and $E^1\Pi$ states have been determined. The values are 0.0153 ± 0.0014, 0.163 ± 0.015, and 0.094 ± 0.009, respectively; $\text{υ′\hspace{0.17em}=\hspace{0.17em}0}$ in each case. Relative intensities in the fourth positive bands have also been determined (and redetermined) at various angles and kinetic energies. Possible variation in relative intensities with scattering angle is discussed. A possible reason is given for the large discrepancy (a factor of 2) between the oscillator strength obtained for the entire fourth positive bands from electron impact and from lifetime measurements by other investigators.