Resonant structure in electron impact excitation of CO near threshold

Abstract

Electron impact excitation functions of numerous states in CO have been measured at 45° scattering angle with resolutions of 16–23 meV FWHM. The decay peak of the 10.04 eV resonance can be seen in the results for the a 3Π, a′ 3Σ+, and A 1Π vibrational levels. There was no evidence of resonant excitation of the a′ 3Σ+ state near 8 eV as suggested by Newton and Thomas. Excitation functions of the b 3Σ+, B 1Σ+, C 1Σ+, c 3Π, and E 1Π states, and a previously unobserbed state at 11.26 eV show numerous sharp resonances in the first few eV above threshold. Energy loss spectra in the 8–14 eV loss region show peaks corresponding to known states as well as to unidentified states. No sign of the metastable state at about 9.5 eV seen by Wells, Borst, and Zipf could be detected in direct excitation, but an indirect excitation process involving the A 1Π state is consistent with the data.

Effect of anisotropic scattering for rotational collisions on electron transport parameters in CO

“…Note that Biagi's cross sections are linearly extrapolated in double logarithmic scale, for energies above 100 eV. The small peak in Biagi's cross section near 6.0 eV is due to a resonance structure in the a 3 Π excitation cross section, as measured by Swanson and co-authors [54]. This peak is not present in the other cross sections sets, probably due to the negligible effect it has on the calculated electron transport parameters in pure CO.…”

Cross Sections for Electron?Carbon Monoxide Collisions in the Range 1?4 eV

“…No changes to the normalization factors could be found which would reduce the discrepancy below this level and it was apparent that it was the electronic excitation cross sections which had to be altered in order to achieve a satisfactory fit to the experimental data. Measurements by Swanson et al (1975) show resonance structure in the a 3 n cross section near threshold. Accordingly we have reduced the a 3 n threshold to 6·01 eV (Krupenie 1966) and incorporated a peak in the cross section near this threshold (see Fig.…”

Absolute differential cross sections for electron-impact excitation of CO near threshold: II. The Rydberg states of CO

“…Nonetheless, a small resonance structure is detected just above the threshold, which we attribute to the 2 + Feshbach resonance at 11.29 eV (figure 1). This Feshbach resonance close to the threshold (11.264 eV) of the j 3 + state is probably the reason for the uncertainties in the determination of the excitation energy of this state (Swanson et al 1975, Middleton et al 1993.…”

“…h Weatherford and Huo (1990). The electronic configuration of this resonance has been taken to be KL1π 4 5σ 3sσ 2 , with the b 3 + state (electronic configuration KL1π 4 5σ 3sσ ) as the parent state (Sanche and Schulz 1972; see also Newman et al 1983, Comer and Read 1971, Swanson et al 1975. state at 10.74 ± 0.02 eV.…”

“…Mazeau et al (1972) measured relative differential cross sections for excitation of the b 3 + and B 1 + states, while Swanson et al (1975) …”