Electron-impact studies of atomic oxygen: I. Differential and integral cross sections; experiment and theory

Abstract

We report both experimental and theoretical differential and integral excitation cross sections of atomic oxygen corresponding to the 2s 2 2p 4 3 P → 3s 3 S (130.4 nm), 2s 2 2p 4 3 P → 3d 3 D (102.7 nm), 2s 2 2p 4 3 P → 3s 3 D (98.9 nm) and 2s 2 2p 4 3 P → 3s 3 P (87.8 nm) transitions at 30, 50, and 100 eV electronimpact energies. Experimental measurements have been made in the angular range from 0 • to 25 • with a conventional electrostatic electron energy-loss spectrometer. The atomic O differential cross sections (DCSs) were put on an absolute scale by normalization to the O 2 DCS values of Johnson and Kanik (2001). Extrapolation of the measured results to larger angles was performed using theoretical calculations as a guide, and integral cross sections were derived. Theoretical calculations based on the R-matrix method, along with other available experimental data, have been compared with the current experimental results.

Electron Collisional Excitation Rates for O i Using the B ‐Spline R ‐Matrix Approach

“…These lines belong to the 3 P-3p 3 P, 5 P, 3 P-1 D, 3 P-3s 5 S o , 3 S o , 3 P-3d 3 D o , 3 P3s 0 3 D o , 3 P-3s 00 3 P o , and 3 P-2s2p 5 3 P o transitions (where 3s, 3s 0 , and 3s 00 represent 2s 2 2p 3 ð 4 S o Þ, 2s 2 2p 3 ð 2 D o Þ, and 2s 2 2p 3 ð 2 P o Þ cores, respectively). Our calculated excitation cross sections show good agreement with the measured cross sections of Doering and coworkers (Gulcicek & Doering 1987Gulcicek, Doering, & Vaughan 1988;Doering & Yang 2001) and Kanik et al (2001) for the resonance 3 P-3s 3 S o , 3 P-3d 3 D o , and 3 P-3s 00 3 P o transitions and differ significantly for the resonance 3 P-3s 0 3 D o and 3 P-2s2p 5 3 P o , intercombination 3 P-3s 5 S o , and forbidden 3 P-3p 3 P transitions, particularly at higher energies.…”

“…The measured excitation cross sections for the resonance 1027, 989, 878, and 792 Å lines and the intercombination line at 1356 Å are also presented by Doering and coworkers (Vaughan & Doering 1987Gulcicek & Doering 1989;Doering & Gulcicek 1989). The absolute excitation cross sections for the resonance lines at 1304, 1027, 989, and 878 Å are also reported by Kanik et al (2001) at 30, 50, and 100 eV using the electron-energy-loss method with uncertainties similar to the recent measurements of the Doering & Yang (2001). Emission cross sections for the 1304 Å line are measured by Noren et al (2001), while the measured emission cross sections for the lines at 1304, 1027, 989, and 878 Å are presented by Wang & McKonckey (1992), Zipf & Erdman (1985), and Zipf & Kao (1986).…”

Accurate cross sections for excitation of resonance transitions in atomic oxygen

“…The ionization continuum was found to contribute 5–15% for the excitation of the 2 p 4 3 P –2 p 3 3 s 3 S o transition and 5–27% for the excitation of the 2 p 4 3 P –2 p 3 3 d 3 D o transition. Good agreement with the experiments of Kanik et al [2001] and Vaughan and Doering [1987] for the 2 p 4 3 P –2 p 3 3 s 3 S o transition was achieved, but discrepancies for the 2 p 4 3 P –2 p 3 3 d 3 D o transition remained. It is clear from three theoretical studies using the RMPS approach that the effect of coupling to the continuum target states is far greater on resonance transitions than on the forbidden transitions in O I.…”

“…The normalization of measured relative cross sections and statistical errors is the major source of uncertainties in the measured direct excitation cross sections. Differential and integral direct excitation cross sections for the resonance lines at 1304, 1027, 989, and 878 Å have been measured by Kanik et al [2001] at 30, 50, and 100 eV using an electron energy loss method. Johnson et al [2003a] recently extended these measurements to lower energies below 30 eV for the 1304 Å line.…”

Ultrastrong Field Ionization ofNen+(n≤8): Rescattering and the Role of the Magnetic Field

“…3(c) and 3(d)] used in this study were taken from data for Ne 4 , Ne 6 , and Ne 7 [32]. Ne , Ne 2 , Ne 3 and Ne 5 excitation cross sections were obtained by scaling isoelectronic cross sections of nearby species O, P, C, N, and Al [32,[36][37][38]. The largest excitation cross sections from the ion ground states were included in this study: Ne (2s 1 2p 62 S, 2s 2 2p 4 3s 2 P, and 4 P), Ne 2 (2s 1 2p 53 P and 2s 2 2p 3 3s 3 S, 2p 6 ), Ne 3 (2s 1 2p 44 P, 2s 2 2p 2 3s 4 P, and 2p 52 P), Ne 4 (2s2p 33 P and 3 S, 2p 43 P), Ne 5 (2s2p 22 P and 2 D, 2s 2 3d 2 D, 2p 32 D, and 2 P), Ne 6 (2s2p 1 P, 2s3d 1 P, and 2p 21 D), and Ne 7 (2p 2 P, 3d 2 D).…”