Mariusz Piwiński

Strontium optical lattice clocks for practical realization of the metre and secondary representation of the second

We present a system of two independent strontium optical lattice standards probed with a single shared ultranarrow laser. The absolute frequency of the clocks can be verified by the use of Er:fiber optical frequency comb with the GPS-disciplined Rb frequency standard. We report hertz-level spectroscopy of the clock line and measurements of frequency stability of the two strontium optical lattice clocks.

Electron-photon coincidence study of the collisional excitation of the Ca state

Experimental values of the electron-impact coherence parameters (EICP) are reported for electron-impact excitation of the state of Ca. The results have been obtained using electron-photon coincidence techniques for incident electron energies of 45 and 60 eV and scattering angles of and . EICP values determined at 45 eV are compared with similar data obtained by other groups with coincidence and optical pumping methods. Our data do not show a disagreement with the theoretical calculations based on a relativistic distorted-wave approximation (RDWA) that was reported for earlier experimental coincidence results.

Coincidence study of excitation of cadmium atoms by electron impact

We present experimental values of the electron impact coherence parameters (EICP) and reduced Stokes parameters for excitation of 51P1 state of cadmium atoms. The results have been obtained using electron–photon coincidence technique for incident electron energies 80 eV and 60 eV and electron scattering angles in the range of 5° to 50°. We also present an additional set of data for electron energy 100 eV and scattering angle 50° which complements our previous results. All the experimental values are compared with theoretical relativistic distorted-wave approximation (RDWA) calculations. The first Born approximation (FBA) predictions of the alignment angle are also presented. The theoretical results are in good qualitative agreement with the experimental data.

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.

Coincidence measurements of electron-impact coherence parameters for e-He scattering in the full range of scattering angles

Electron impact coherence parameters for inelastic e-He scattering have been measured for the excitation to the 2 {sup 1}P{sub 1} state at collision energy of 100 eV. The experiment was conducted using angular correlation electron-photon coincidence technique with a magnetic angle changer allowing measurements in full range of scattering angles. The results are compared with other experimental data and theoretical predictions available for this collisional system.

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.

Two independent strontium optical lattice clocks for practical realization of the meter and secondary representation of the second

We report a system of two independent strontium optical lattice standards probed with a single shared ultra-narrow laser. This allows verification of relative stability of both optical standards. The absolute frequency of the clocks can be roughly verified by the use of an optical frequency comb with the GPS-disciplined Rb frequency standard or, more accurately, by a long distance stabilized fiber optic link with the UTC(AOS) and UTC(PL) via the OPTIME network.

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