J. K. Swenson

Surgery of fast, highly charged ions studied by zero-degree auger spectroscopy

Abstract Zero-degree Auger spectra were measured for the projectile in collisions of oxygen and carbon on He with incident charge states of q = 2–5 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 of single excitation and single loss, two-electron processes such as transfer excitation and transfer loss are studied.

Studies of electron correlation effects in multicharged ion atom collisions involving double capture

We review measurements of L-Coster Kronig and Auger electron production in slow, multicharged collision systems to study electron correlation effects in the process of double electron capture. The n/sup /minus/3/ law was confirmed for the production of the Coster-Kronig configurations 1s/sup 2/2pn/ell/ (n greater than or equal to 6) in O/sup 6 +/ + He collisions. Enhancement of high angular momentum /ell/ in specific 1s/sup 2/2pn/ell/ configurations was observed by means of high-resolution measurements of the Coster-Kronig lines. The importance of electron correlation effects in couplings of potential energy curves leading to the 1s/sup 2/2pn/ell/ configurations is verified by means of Landau-Zener model calculations. 32 refs., 4 figs.

Evidence for correlated double-electron capture in slow collisions of multicharged ions with He and H2

Abstract High resolution measurements of the production of L 1 L 23 X Coster-Kronig and LMX-Auger electrons in slow collisions of C 4+ , N 5+ , O 6+ , and O 7+ with He and H 2 have been performed, using the method of 0° Auger spectroscopy. For the latter three projectiles, strong Coster-Kronig lines are observed, which are attributed to the configurations (core)2p nl , produced by double-elec- tron capture. It is argued that production of these nonequivalent electron configurations must involve electron-electron correlation. From a comparison of the production cross sections for these Coster-Kronig electrons and the LMX-Auger electrons, it is further argued that correlation plays a significant role in two-electron transfer processes.

Electron correlation effects in collisions of slow, highly charged ions with atoms

Two‐electron processes produced by electron‐electron interaction in collisions of slow, highly charged ions with atoms are reviewed. These dielectronic processes are observed as manifestations of dynamic electron correlation in the collision systems 60‐keV O6++He and 60‐keV C6++He. In particular, the dielectronic process of autoexcitation is shown to create the configurations 2lnl ’ (n≥3) of non‐equivalent electrons. Instrumental problems due to the detection of low‐energy Coster‐Kronig electrons in O6++He collisions, can be resolved by measuring K‐Auger electrons in the C6++He system. Calculated mean Auger yields are found to deviate significantly from unity in C6++He collisions indicating that stabilization effects are important for that system. Recent measurements of angular distribution of the K‐Auger electrons are shown to provided evidence for alignment effects in the state attributed to 2l3l ’ and 2l4l ’.

Excitation curve for Auger decay of the (1s2s2p2)3D state of C2+ formed through RTE☆

Abstract The ORNL EN tandem supplied beams of 3.5–9 MeV C 3+ ions which were incident on a differentially pumped He target. Auger electrons emitted by fast C 2+ ions emerged at 10° (lab) w.r.t. the incident ion beam. They were detected using a two stage spectrometer with kinematic refocusing. An excitation curve was obtained for the (1s2s2p 2 ) 3 D state Auger decay to the ground state of C 3+ . The excitation curve peaks at ~ 6 MeV, which strongly supports the notion that the state is formed through resonant transfer and excitation.

Correlated double electron capture in slow, highly charged ion-atom collisions

Abstract Recent measurements [1,2] of autoionization electrons produced in slow, highly charged ion-atom collisions are reviewed. Mechanisms for double electron capture into equivalent and nonequivalent configurations are analyzed by comparing the probabilities for the creation of L-Auger electrons and L1L23X Coster-Kronig electrons. It is shown that the production of the Coster-Kronig electrons is due to electron correlation effects whose analysis leads beyond the independent-particle model. The importance of correlation effects on different capture mechanisms is discussed.

Transfer and excitation processes studied in H-like S and Li-like and H-like F colliding with H2

Abstract We have studied transfer and simultaneous excitation by three different experimental techniques. Coincidences between two K X-rays were measured for S15+, as well as coincidences between one K X-ray and the charge-exchanged projectile for Li-like F and projectile Auger electrons for H-like F, in each case colliding with H2. For all three collision system, the measured cross sections are dominated by resonant transfer and excitation (RTE). Also, for the F projectiles, strong contributions from two-electron transfer and excitation (2eTE) were found.