Collisions between antiprotons and matter are of fundamental interest in atomic physics. In the last decade a number of theories had been developed and applied to the description of experimental cross sections. The theoretical works focused on the calculation of the total cross sections in view of the current lack of experimental data for differential ones.

We present theoretical total, singly- and doubly-differential ionization cross sections in collisions between antiprotons and helium atoms at slow antiproton impacts. The calculations were performed within the frame work of the continuum distorted wave eikonal initial state approximation and a three-body classical trajectory Monte Carlo (CTMC) method. Our results are compared with other theoretical approaches and with experimental data. We find clear evidence for the formation of the anti-cusp in the differential distributions.

As a result of the exotic Rydberg atom formation, we also present state-selective (n, l) capture cross sections of antiprotons by 3He and 4He atoms. The calculations were based on the 3-body CTMC method. We demonstrate that the classical approximation of the collision describes the capture cross sections with considerable success. We show that the resulting (n, l) distributions of captured antiprotons are in reasonable agreement with the measurements.

 

Title 2: Guiding of slow highly charged ions through a single mesoscopic capillary

Abstract:

We present systematic measurements in collisions between slow highly charged ions and a macroscopic glass capillary with large aspect ratio. The observed data strongly support that the guiding effect known from nanocapillaries is also valid up to macroscopic dimensions of the order of millimeter. Possible tilt angles were as large as about 5° for still significant transmission. The charging-up of the insulating wall can be observed in time-dependent transmission measurements. The angular distributions of the transmitted ions have a similar width as the incident beam. Eventually, the usage of such micro-capillaries could be an interesting alternative ion-optical tool for various applications, especially where the size, the costs or the accessibility are a critical factor. Finally, we also will show, as a completely new aspect for the deeper fundamental understanding of the guiding phenomenon, the first temperature dependent measurements for guiding.

 

Dr. Károly TŐkési is the scientific adviser of Institute of Nuclear Research of the Hungarian Academyof Sciences. His research experience was in Electronoptics, Electron spectroscopy, Electron-atom, ion-atom collision studies, Classical Trajectory Monte Carlo calculations, Electron energy loss spectroscopy,XPS and Auger spectroscopy, Simulation of electron spectra using Monte Carlo techniques,Experiences in developing programs using FORTRAN programming languages. Presently he is working on the Studies of the interactions of highly charged ions with surfaces, Investigation of the energy loss of ions in grazing interaction with the capillary walls and Investigation of laser-atom, laser-molecule collisions. He has 3 book chapters and 203 publications in referred journals or volumes including PRL,PRA, PRB, and nuclear related, etc.