14 research outputs found
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Dielectronic recombination measurements on multicharged ions
Coaxial electron beams and multiply charged ion beams are used to study dielectronic recombination. The study includes recombination of boron, carbon and sulfur. 3 refs., 7 figs. (WRF
L
Article discussing research on L- and M-shell x-ray production cross sections of Nd, Gd, Ho, Yb, Au, and Pb by 25-MeV carbon and 32-MeV oxygen ions
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Dielectronic recombination measurements in a single pass experiment
Until 1983 the only experimental information on DR had come from spectroscopic observations of plasmas from which only thermally averaged rates may be inferred. In 1983-84 four groups reported DR cross section measurements. A group at the joint Institute for Laboratory Astrophysics (JILA) measured the DR cross section of Mg/sup +/ using crossed ion-electron beams and recording coincidences between recombined Mg atoms and stabilizing photons from the collision region. A similar experiment was carried out by Williams for Ca/sup +/. Two groups used merged electron-ion beam methods (i.e. similar in geometry to electron beam cooling systems). One experiment at the University of Western Ontario used a tenuous; emission limited, highly monoenergetic electron beam merged with a 450 keV C/sup +/ beam to reach the requisite collision energies of a few eV; (the signal levels here were very low). At Oak Ridge National Laboratory (ORNL) we wish to work with multiply charged ions and we have chosen to use a compressed space charge limited electron beam. We chose a merged beam approach to take advantage of our ability to produce high charge state, MeV/amu ions and a high current, high energy (1-3 keV) electron beam. The merged beam apparatus is constructed such that in the interaction region, the ion beam is coaxial with and embedded within the electron beam for a distance of 84 cm. 6 references, 8 figures
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Dielectronic recombination of multiply charged ions
Using a merged electron-ion merged beam apparatus in conjunction with the ORNL EN Tandem Van de Graaff, we have measured dielectronic recombination in ..delta..n = 0 transitions for a number of Li-liked (B/sup 2 +/, C/sup 3 +/, N/sup 4 +/, and O/sup 5 +/), Be-like (C/sup 2 +/, N/sup 3 +/, and O/sup 4 +/), B-like (N/sup 2 +/, O/sup 3 +/, and F/sup 4 +/), and Na-like (P/sup 4 +/, S/sup 5 +/, and Cl/sup 6 +/) ions. The results are compared with theory which includes field enhancement and extension of the more highly charged ions is discussed. 11 refs., 11 figs
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Production of autoionizing Rydberg states by transfer excitation in high energy ion atom collisions
The method of zero-degree Auger spectroscopy was used to study the production of autoionizing Rydberg states in collisions of carbon and oxygen projectiles incident at several MeV on He gas and carbon foils. The autoionization electrons were measured with high resolution so that the quantum defect corresponding to the angular momenta of the Rydberg electrons could be observed. The main purpose of the present experiment is to gain information about the n and l distribution of the Rydberg electron captured in the collision. The well-known n/sup -3/ law is confirmed. For the He gas target it is found that the angular momenta p and d are predominantly produced. For the foil target the higher angular momenta are clearly enhanced. 15 refs., 6 figs
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Observation of resonant transfer and excitation in O/sup 5 +/ + He collisions through high resolution O/sup 0/ Auger electron spectroscopy
In this paper we present new evidence that (resonant transfer and excitation) RTE is an important mechanism for the production of Be-like doubly excited states in energetic collisions of Li-like O/sup 5 +/ ions incident on He. We have measured the cross sections for the production of Auger electrons from the decay of the (1s2s2p/sup 2/)/sup 3/D and the (1s2s2p/sup 2/)/sup 1/D states in O/sup 4 +/ in high resolution at O/sup 0/, as a function of the incident ion energy. We observe a resonant increase in the Auger cross section with a maximum at approx.13 MeV and full-width-at-half-maximum of approx.7 MeV. This feature is seen to sit on a non-resonant NTE background, which populates the same intermediate states through a two step capture and excitation process governed by the electron-nucleus Coulomb interaction. 13 ref., 3 figs
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Surgery of fast, highly charged ions studied by zero-degree Auger spectroscopy
Zero-degree Auger spectra were measured in collisions of oxygen and carbon on He with incident charge states of q = 2 to 5 and for energies from 5 to 30 MeV. Since the light target particle He acts selectively on the projectile ion, we refer to the present method as ion surgery. Apart from the one-electron processes single excitation and single loss, two-electron processes such as transfer excitation and transfer loss are studied. 17 refs., 4 figs., 1 tab
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Electron Transfer Processes in Collisions of Highly Charged Energetic (0.1 to 1.0 MeV/nucleon) Ions with Helium Atoms
We have investigated charge transfer in collisions of energetic (0.1 - 1 MeV/nucleon) highly charged ions with helium atoms with the principal aim clarifying the nature of two-electron processes. The sensitivity of partial charge-changing cross sections (i.e., single- and double-charge transfer, transfer ionization (TI), and single and double ionization) to core configuration and scaling rules for one- and two-electron processes were investigated with iodine ions (q = 5+ ..-->.. 26+) and uranium ions (q = 17+ ..-->.. 44+) using an ion-charge state, recoil-ion coincidence method. Using zero-degree electron spectroscopy in coincidence with charge transfer, we found that at the higher energies, as in the case of 0.1 MeV/nucleon ions previously reported, TI involves the transfer of two electrons to a higher correlated state followed by loss of one electron to the continuum. In addition, we observe very high Rydberg electrons in coincidence with TI, implying a possible up-down correlation in the pair transfer. In addition, we made measurements of VUV photons emitted at the collision in coincidence with He/sup +/ and He/sup 2 +/ recoils. The results show that TI leads to capture into lower n states than single-charge transfer. 15 refs., 10 figs
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L- and M-shell x-ray production cross sections of Nd, Gd, Ho, Yb, Au, and Pb by 25-MeV carbon and 32-MeV oxygen ions
Article discussing research on L- and M-shell x-ray production cross sections of Nd, Gd, Ho, Yb, Au, and Pb by 25-MeV carbon and 32-MeV oxygen ions
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M-Shell Electron Capture and Direct Ionization of Gold by 25-MeV Carbon and 32-MeV Oxygen Ions
M-shell x-ray production cross sections have been measured for thin solid targets of Au for 25 MeV /sup 12/C/sup q+/ (q = 4, 5, 6) and for 32 MeV /sup 16/O/sup q+/ (q = 5, 7, 8). The microscopic cross sections were determined from measurements made with targets ranging in thickness from 0.5 to 100 ..mu..g/cm/sup 2/. For projectiles with one or two K-shell vacancies, the M-shell x-ray production cross sections are found to be enhanced over those by projectiles without a K-shell vacancy. The sum of direct ionization to the continuum (DI) and electron capture (EC) to the L, M, N ... shells and EC to the K-shell of the projectile have been extracted from the data. The results are compared to the predictions of first Born theories i.e. PWBA for DI and OBK of Nikolaev for EC and the ECPSSR approach that accounts for energy loss, Coulomb deflection and relativistic effects in the perturbed stationary state theory. 25 references, 3 figures, 1 table