Absolute-rate coefficient forC3+(2s→2p) electron-impact excitation
| Autor: | Daniel Wolf Savin, John L. Kohl, A. R. Young, D. B. Reisenfeld, L. D. Gardner |
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| Rok vydání: | 1995 |
| Předmět: | |
| Zdroj: | Physical Review A. 51:2162-2168 |
| ISSN: | 1094-1622 1050-2947 |
| DOI: | 10.1103/physreva.51.2162 |
| Popis: | We have measured the absolute-rate coefficient for electron-impact excitation (EIE) of ${\mathrm{C}}^{3+}$(2s $^{2}$${\mathit{S}}_{1/2}$\ensuremath{\rightarrow}2p $^{2}$${\mathit{P}}_{1/2,3/2}$) for energies near threshold. A delayed coincidence technique with inclined beams was used. Radiation from the excited ions was detected using an optical system that subtends slightly over \ensuremath{\pi} steradians. At an ion-rest-frame energy of 10.10 eV the measured rate coefficient was (7.79\ifmmode\pm\else\textpm\fi{}2.10)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}8}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ and the measured cross section was (4.15\ifmmode\pm\else\textpm\fi{}1.12)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}16}$ ${\mathrm{cm}}^{2}$. The uncertainties quoted here represent the total experimental uncertainty, statistical and systematic, at a confidence level considered to be equivalent to a statistical 90% confidence level. Good agreement is found with other measurements. Agreement is not good with Coulomb-Born with exchange and two-state close-coupling calculations, both of which fall outside our 90% confidence limits. Nine-state close-coupling calculations are in better agreement. However, the calculations lie at the extreme edge of our uncertainty limits. Taking into account previous measurements of EIE in ${\mathrm{C}}^{3+}$ and also a measurement of EIE in Li-like ${\mathrm{Be}}^{+}$ that falls significantly below theory at threshold, there is a suggestion that the ${\mathrm{C}}^{3+}$(2s\ensuremath{\rightarrow}2p) EIE rate coefficient near threshold may fall slightly below presently accepted values. |
| Databáze: | OpenAIRE |
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