V. Karaganov

Sub-Doppler bandwidth atomic optical filter.

We demonstrate what is to our knowledge the first atomic optical filter that uses velocity selection to achieve a passband width that is less than the Doppler width of the filtering transition. A narrow-linewidth pump laser is used to induce circular birefringence in a narrow velocity class of atoms in a dense potassium vapor for 694-nm light resonant with the 4P(3/2)-6S(1/2) transition. The filter displays a single 170-MHz passband at a peak transmittance of 9.5%. The bandwidth is an order of magnitude lower than that of previously demonstrated atomic optical filters.

Superelastic electron - lithium scattering at 7 and 14 eV

We present results from a joint theoretical and experimental investigation of electron-impact-induced lithium transition at 7 and 14 eV. The experiment employs the superelastic technique to measure the Stokes parameters , and over the angular range of to , yielding statistical errors of only a few per cent. The convergent close-coupling theory obtains complete agreement with the full set of measurements.

SUPERELASTIC ELECTRON SCATTERING FROM POTASSIUM

Measurements of the orientation and alignment parameters have been performed on potassium atoms using a superelastic scattering technique. In these experiments a laser beam is tuned to the transition in potassium. Electrons are scattered from these excited atoms and those electrons that gain energy in the collision are detected. These superelastic electrons carry information about the orientation and alignment parameters which describe the scattering process. Orientation and alignment parameters have been measured at an electron energy of 10 eV referred to the ground state and over an angular range from to . These parameters are in excellent agreement with those predicted using the convergent close-coupling theory.

ELECTRON IMPACT EXCITATION OF THE 42P STATE IN POTASSIUM AT 54.4 EV : DIFFERENTIAL CROSS SECTIONS, ALIGNMENT AND ORIENTATION PARAMETERS

A complete set of spin-averaged parameters, including the differential cross sections and three Stokes parameters, were obtained from a series of superelastic scattering experiments on the 4 2P state in potassium. The four scattering parameters have been measured at an effective electron energy of 54.4 eV on the ground state and over an angular range from 0° to 145°. The experimental results are compared with a convergent close-coupling (CCC) calculation and several distorted-wave calculations together with previously reported measured differential cross sections. The excellent agreement between the CCC theory and the present measurements resolves a long-standing anomaly between theory and experiment at this energy in potassium.

Super elastic electron scattering from alkali atoms

The results from the super elastic electron scattering experiments on lithium and potassium that have been carried out at Flinders University over the past decade are reviewed and compared with the predictions of the CCC theory of Bray. We find that there is excellent agreement between theory and experiment over a wide range of energies in lithium. The agreement in the case of potassium is very good. We present the first results for orientation and alignment parameters for electron scattering from cesium. Our preliminary results at 10 eV show that relativistic effects are very small.

Coherence and correlation in electron scattering from the alkalis

A series of superelastic electron scattering experiments from lithium and from potassium is described in which the total polarisation parameter P+ is measured. We report significant departures from the coherence condition P+ = 1 for both targets. The structure observed in the parameter P+ can be interpreted by a qualitative wave mechanical model that had been introduced by our research group to explain similar structure in superelastic electron scattering experiments from sodium.

Laser assisted collisions of electrons with metal vapours

Three separate experiments are described which use laser radiation to probe the details of electron scattering processes from metal vapour targets. Results from superelastic scattering experiments from calcium are presented. The experiments were carried out at incident energies of 25·7 and 45 eV referred to the ground state. Scattering amplitudes derived from these experiments demonstrate that current theories are inadequate. The coherence of the excitation process has been studied by measuring the total polarisation. It is shown that the excitation process is coherent over the whole kinematic range. Preliminary results from a study of superelastic electron scattering from lithium are discussed where it is shown that a quantum electrodynamical model can be used to describe the optical pumping process in 6Li and 7Li. In addition the first superelastic electron spectrum is presented for experiments on lithium. A stepwise excitation technique is described with which cross sections for the electron impact excitation of the 3d9 4s2 2D state in copper can be measured. The experiments are complicated by the presence of D states in the incident copper beam. The origin of these D states is described as is a modification of the technique which leads to their removal.