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Title: Absolute cross section for C{sup 2+}(2s2p {sup 3}P{sup o}{yields}2p{sup 2} {sup 3}P) electron-impact excitation

Abstract

We have measured the absolute energy-averaged cross section for the electron impact excitation of C{sup 2+}(2s2p {sup 3}P{sup o}{yields}2p{sup 2} {sup 3}P) from energies below threshold to 17 eV above, and present the measured absolute rate coefficients for this transition, for temperatures from 10{sup 4} to 10{sup 5} K. These rate coefficients are required for diagnostics of plasmas such as those found in astrophysical environments. The synchronous photon detection method with beams modulation and inclined electron and ion beams was used. Radiation at 117.6 nm from the decay of the excited ions back to the metastable state was detected using an absolutely calibrated optical system. The fractional population of metastable C{sup 2+}(2s2p {sup 3}P{sup o}) in the incident ion beam was determined to be 0.42{+-}0.03(1.65 {sigma}). The rate coefficient for log{sub 10} T=4.8 was determined to be 1.01x10{sup -8} cm{sup 3} s{sup -1}{+-}14% at a 90% confidence (1.65 {sigma}) level. The measured cross section is in agreement within experimental uncertainty with 6-term close-coupling R-matrix calculations and 90-term R matrix with pseudostates calculations.

Authors:
; ; ;  [1]
  1. Harvard-Smithsonian Center for Astrophysics, Cambridge, Masssachusetts 02138 (United States)
Publication Date:
OSTI Identifier:
20786915
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 73; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.73.032709; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; CARBON; CARBON IONS; CATIONS; COUPLING; CROSS SECTIONS; DECAY; DETECTION; ELECTRON-ATOM COLLISIONS; ELECTRONS; EV RANGE; EXCITATION; ION BEAMS; METASTABLE STATES; MODULATION; OPTICAL SYSTEMS; PHOTONS; PLASMA; R MATRIX

Citation Formats

Daw, A., Gardner, L. D., Janzen, P. H., and Kohl, J. L. Absolute cross section for C{sup 2+}(2s2p {sup 3}P{sup o}{yields}2p{sup 2} {sup 3}P) electron-impact excitation. United States: N. p., 2006. Web. doi:10.1103/PHYSREVA.73.0.
Daw, A., Gardner, L. D., Janzen, P. H., & Kohl, J. L. Absolute cross section for C{sup 2+}(2s2p {sup 3}P{sup o}{yields}2p{sup 2} {sup 3}P) electron-impact excitation. United States. doi:10.1103/PHYSREVA.73.0.
Daw, A., Gardner, L. D., Janzen, P. H., and Kohl, J. L. Wed . "Absolute cross section for C{sup 2+}(2s2p {sup 3}P{sup o}{yields}2p{sup 2} {sup 3}P) electron-impact excitation". United States. doi:10.1103/PHYSREVA.73.0.
@article{osti_20786915,
title = {Absolute cross section for C{sup 2+}(2s2p {sup 3}P{sup o}{yields}2p{sup 2} {sup 3}P) electron-impact excitation},
author = {Daw, A. and Gardner, L. D. and Janzen, P. H. and Kohl, J. L.},
abstractNote = {We have measured the absolute energy-averaged cross section for the electron impact excitation of C{sup 2+}(2s2p {sup 3}P{sup o}{yields}2p{sup 2} {sup 3}P) from energies below threshold to 17 eV above, and present the measured absolute rate coefficients for this transition, for temperatures from 10{sup 4} to 10{sup 5} K. These rate coefficients are required for diagnostics of plasmas such as those found in astrophysical environments. The synchronous photon detection method with beams modulation and inclined electron and ion beams was used. Radiation at 117.6 nm from the decay of the excited ions back to the metastable state was detected using an absolutely calibrated optical system. The fractional population of metastable C{sup 2+}(2s2p {sup 3}P{sup o}) in the incident ion beam was determined to be 0.42{+-}0.03(1.65 {sigma}). The rate coefficient for log{sub 10} T=4.8 was determined to be 1.01x10{sup -8} cm{sup 3} s{sup -1}{+-}14% at a 90% confidence (1.65 {sigma}) level. The measured cross section is in agreement within experimental uncertainty with 6-term close-coupling R-matrix calculations and 90-term R matrix with pseudostates calculations.},
doi = {10.1103/PHYSREVA.73.0},
journal = {Physical Review. A},
number = 3,
volume = 73,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
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  • Absolute total cross sections for electron-impact excitation of the 2s{sup 2}S{r_arrow}2p{sup 2}P transition in C{sup 3+} were measured from 7.35 eV to 8.45 eV using the merged electron-ion-beams energy-loss technique. The results settle the discrepancy between two previous experiments using the crossed-beams fluorescence method, being in very good agreement with the older results [P. O. Taylor, D. Gregory, G. H. Dunn, R. A. Phaneuf, and D. H. Crandall, Phys. Rev. Lett. {bold 39}, 1256 (1977)] but less so with the more recent ones [D. W. Savin, L. D. Gardner, D. B. Reisenfeld, A. R. Young, and J. L. Kohl, Phys.more » Rev. A {bold 51}, 2162 (1995)]. The present measurements are also in good agreement with unitarized Coulomb-Born and close-coupling calculations. {copyright} {ital 1998} {ital The American Physical Society}« less
  • Double differential cross sections of doubly excited autoionizing (2p{sup 2}){sup 1}D and (2s2p){sup 1}P states due to 150 eV-1 keV electron, 100 keV-1.5 MeV H{sup +}, 400 KeV-1.6 MeV He{sup +} and He{sup ++} impact on He were measured at zero degree observation angle. Two electrostatic spectrometers were used in tandem where the first analyzer separates the emitted electrons from the incident projectile beam and the second analyzer provides high resolution performance. The projectile beam was tightly collimated and then traversed a 9 mm long gas cell containing 20 mT He gas. All measurements have been performed under single collisionmore » conditions. Strong interference effects between resonance lines and direct ionization continuum are evident in the observed spectra in particular for slower positive projectile ions due to strong Coulomb Interaction in the Final States (CIFS). Our double differential cross sections have been absolutely calibrated using the theoretical and semiempirical single ionization data given by Kim and Rudd. The experimental results are compared with theoretical calculations including three CFIS.« less
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