Collisions of highly charged ions with electrons, atoms and surfaces

At the Oak Ridge Multicharged Ion Source Facility, an experimental atomic collisions physics program is centered around a recently upgraded Electron Cyclotron Resonance (ECR) multicharged ion source. The 10 GHz CAPRICE source has been in operation since October 22, 1992, and has provided more intense, higher charge ion beams than our previous ECR ion source. Intense metallic beams have recently become available with the installation of a metallic oven on the source. In addition to measurements of electron-impact excitation, carried out in collaboration with the Joint Institute for Laboratory Astrophysics (JILA), experiments are presently on-line to study electron-impact ionization, low-energy ion-atom collisions, and ion-surface interactions. A brief summary of our various activities with an emphasis on the new capabilities is presented

Adiabatic theory of Wannier threshold laws and ionization cross sections

The Wannier threshold law for three-particle fragmentation is reviewed. By integrating the Schroedinger equation along a path where the reaction coordinate R is complex, anharmonic corrections to the simple power law are obtained. These corrections are found to be non-analytic in the energy E, in contrast to the expected analytic dependence upon E

Detection of hepatitis C core antigen in serum or plasma as a marker of hepatitis C viraemia in the serological window-phase.

A new immunoassay for the detection of hepatitis C core antigen (HCVcoreAg) in peripheral blood during serological window-phase was evaluated among healthy blood donors, commercially available hepatitis C virus (HCV) seroconversion panels and in-house specimens from individuals undergoing seroconversion. Among 1964 low-risk blood donor samples, seven samples were initially reactive but only one was repeat reactive. Reactivity of this specimen was not confirmable by neutralization with specific anti-HCV core antibody, and the sample was negative for HCV RNA by polymerase chain reaction (PCR). The specificity of the HCVcoreAg enzyme-linked immunosorbent assay (ELISA) was 99.95%. In seven commercially available HCV seroconversion panels, HCVcoreAg appeared 23-46 days earlier than anti-HCV antibody by third generation assay. Additional testing with specimens from patients undergoing anti-HCV seroconversion indicated that HCVcoreAg becomes undetectable by the present test format soon after the onset of antibody. This test may be considered as an alternative to nucleic amplification techniques (NAT) for blood donor HCV screening. Additional development of technology for detecting HCVcoreAg may be useful for patient diagnosis and therapy monitoring