Łukasz Kłosowski

Magnetic angle changer?a new device allowing extension of electron?photon coincidence measurements to arbitrarily large electron scattering angles

The electron–photon coincidence technique has been used as the most sensitive tool for investigating inelastic collisions of atoms with electrons and heavy particles and led to new insights into collision dynamics theory. However, for purely geometrical reasons, due to finite sizes of the electron energy analysers and electron beam sources, the measurements have not been carried out for the largest scattering angles. We present a novel system for electron–photon coincidence experiments on electron inelastic scattering with the magnetic angle changer allowing determination of excitation parameters at arbitrarily large scattering angles. As shown by experimental tests, our device can be successfully used in the electron–photon coincidence experiment and it has unprecedented efficacy—deflection angle up to 60° for 100 eV electrons, without a ferromagnetic core.

Nonlinear resonances in linear segmented Paul trap of short central segment

Linear segmented Paul trap system has been prepared for ion mass spectroscopy experiments. A non-standard approach to stability of trapped ions is applied to explain some effects observed with ensembles of calcium ions. Traps stability diagram is extended to 3-dimensional one using additional ∆a besides standard q and a stability parameters. Nonlinear resonances in (q,∆a) diagrams are observed and described with a proposed model. The resonance lines have been identified using simple simulations and comparing the numerical and experimental results. The phenomenon can be applied in electron-impact ionization experiments for mass-identification of obtained ions or purification of their ensembles.

Electron impact ionization of calcium atoms inside quadrupole trap

Loading a Paul trap with ions requires application of ionization process of any type. In the case of calcium ions, two photoionization schemes [1, 2] are commonly used. High-energy (keV) electron impact technique was also used before development of the optical methods. Our experimental results confirmed that the electronic ionization can be relatively easily achieved for energies below 100 eV. The proposed technique provides ion production rate at the level of hundreds of new ions per second. An efficiency of ionization strictly depends on experimental conditions such as energy and density of the electron beam, atomic beam density and trapping potential parameters. Thus, analysis of the cloud of trapped ions for given conditions delivers information about integral cross sections for electron impact ionization processes. The ion production rate is given by equation:

Energy and momentum transfer in electron-ion elastic collisions

A new experimental setup using ion trap with electronic beam for ionization process was applied for investigation of trapped ions [1]. There are two interesting phenomena connected with such technique: heating of the trapped ions by Coulomb interactions between ions and the incoming electrons and pressure of electrons acting on the trapped ion cloud. Only the former was observed in the experiment. The experiment has been performed in a Paul trap with Ca+ ions as a target. The experimental procedure includes loading the trap by electron-impact ionization of calcium atoms at chosen collision energy. After cutting off the electronic and atomic beams, the trapped ions are Doppler-cooled to the temperature below 1 mK using 397 nm and 866 nm laser beams. They are detected by observation of 397 nm fluorescence using a CCD camera. After introduction of electron beam to the ion cloud, the image of the ion ensemble becomes less explicit, which can be explained by increase in amplitude of ion motion in the trap’s potential well. Example of such effect is presented in Fig. 1. Shifting of ion cloud was not observed.

Integral electron impact ionization cross section of molecules through Coulomb crystallization of the product ions

We present a new method for measuring electron impact ionization cross section of molecules through Coulomb crystallization of the product ions in a linear Paul trap.. The idea of electron impact ionization cross sections measurements is described, and the technique is analyzed in terms of its efficiency and some specific apparatus effect