Effect of experimental parameters on resonance fluorescence of a polarized atomic-sodium beam

L. Yu. Khryashchev

Xian-Kun Meng

The resonant excitation of the sodium D2 transition by laser radiation was investigated experimentally in this thesis. Line polarization measurement of the resonance fluorescence was employed to investigate the excitation process. The sodium atoms, which were collimated in a very narrow beam, were excited by a monochromatic laser beam with the frequency tuned to resonance with the 32S 112(F=2) - 32P312 hyperfine transition. The direction of the laser beam was perpendicular to the atomic beam and the fluorescence photons were detected along a direction perpendicular to both the laser and atomic beams. The experimental measurements were performed to determine the effect due to the variation of the laser intensity and frequency on the line polarization. A theoretical expression of the line polarization as a function of density matrix elements of the upper excited hyperfine sub -states was derived. A full quantum electrodynamic theory was used to derive an atomic operator equation of motion which was needed to calculate atomic operator elements. These elements then yielded the corresponding density matrix elements. The experimental results and the theoretical modelling were in a good agreement. The first experimental results for the line polarization of the highly excited states, 42D512 and 42D312, are also presented. The use of two lasers enabled these highly excited states to be excited. The line polarization of the fluorescence for transitions from the 4D level down to lower states is derived in terms of the density matrix elements of the upper excited states. Two limiting cases for the theoretical predictions of the line polarization are considered.

M. Elbel, B. Niewitecka, L. Krause

The Hanle effect, which is commonly exhibited by atoms that emit resonance fluorescence while in a magnetic field, has been observed in sensitized fluorescence of sodium vapor. The sodium atoms were excited by σ+ polarized D1 radiation which produced a vector polarization in the 32P1/2 state, and were then transferred to the 32P3/2 state by collisions with helium atoms. The fluorescence was observed at an angle of 325° to the direction of excitation, and the magnetic field was perpendicular to the directions of the exciting and fluorescent light beams. The addition of helium resulted in the appearance of a circularly polarized D2 component in the fluorescent light. The polarization of the sensitized fluorescence decreased with increasing field as in the ordinary Hanle effect but the width of the Hanle signal was smaller than that observed in resonance fluorescence. The observed narrowing effect is in good agreement with theoretical predictions.

Barry L. Sharp, A. Goldwasser

Muhammad Abdul-Hakim Bukhari, H -J Beyert, M. A. Chaudhry +3 more

A beam of unpolarized electrons is crossed at right angles with a beam of partially polarized sodium or potassium atoms (degree of polarization P A approximately=21%) and resonance lines from the excited 2 P 3/2, 1/2 states are observed in a direction perpendicular to both the atom and electron beams for electron energies from threshold to 200 eV. The polarization of the emitted photons is measured in the form of the Stokes parameters P 1 , P 2 and P 3 . The present measurements for sodium atoms are in better agreement with the theoretical values than the previously published experimental results. No other experimental or theoretical results are available for potassium atoms.

V. N. Rebane