Polarization degrees were measured for 8 Mg lines excited by an electron beam with an energy up to 300eV. The crossed beam technique was used. The atomic beam density was below 1011cm-3, and the electron current density did not exceed A/cmZ. The analysis of the polarization degree due to transitions 3lP-n'D for n = 4 through 9 is given on the basis of the Born calculations. The features of cross sections are also compared with those of polarization in the series.
An interpolation formula is proposed for the degree of polarization of S-P and P-D radiation of atom and ion transitions induced by electron collisions. The formula describes well theoretical calculations and experimental data. Similarities in the polarization of the resonance S-P transitions of hydrogen- and helium-like atomic systems are analyzed.
The optical excitation functions of 15 lines and the polarization degree of 6 lines of Ba' ions were measured using crossed beams of electrons and neutral barium atoms. The electron impact energy was varied from the threshold up to 300eV. The atomic density was less than 5 x 1010cm-3. Nine excitation functions were measured for the first time. The excitation cross-sections of the ionic lines were obtained relative to that of the atomic resonance line 6 IS-6 ' P (5535 A), normalized to the Bethe theory in the high-energy limit. Measured cross-sections for the 6 'S1,,-6 'P,,, and 6 'P,/,-7 2S,i, transitions are compared with other experimental results. The total uncertainties vary from 10% for the 6 'S-6 *P up to 46% for the 6 'P3,,-7 'D,/, and 6 'P,/,-8 'SIi, cross-sections. The polarization degree of 5 ionic lines were measured for the first time. The polarization function of each line exhibits oscillatory structure in the threshold region.* E , is the threshold energy; E , the energy corresponding to the maximum value of the cross-section; Q , the maximum value of the cross-section and Qe the cross-section at E E 30eV.
A procedure for the experimental spectropolarimetry of atoms is described.
This procedure is realized within the framework of the ‘full polarization
beam experiment’. It is based on the theory developed with the use of the
mathematics of the atom density matrix. The density matrix components ρ0(0) and ρ2(2) and the parameter
of state alignment A(2)
were measured experimentally for the first time. These parameters fully
characterize the excitation of the atomic state alignment by electron impact.
Experimental results for a number of states of the magnesium atom as well as
for the singly charged magnesium and barium ions are first presented.
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