Eine Methode zur Bestimmung des Verhältnisses σ _T /σ _S =α der totalen Streuquerschnitte für Streuung von Alkaliatomen thermischer Energie am Triplett- und am Singulettpotential

Abstract

It has been proved experimentally that the flux of atoms emerging through a hole from a cell containing Rubidium vapour depends on the vapour's spin polarisation.

The dimensions of the cell have been smaller than the mean free path of the atoms in order to avoid multiple collisions. The atoms emerged from the cell through a system of aligned slits; the atomic flux was measured by means of a Langmuir-Taylor-Detector. A sufficiently large slit in the rear of the cell opposite to the beam-forming system of slits assured that no atoms in the beam could come from collisions with the cell surface. Hence all atomic particles had to come from interatomic collisions which happened inside the volume of vapour. As these atoms were polarized by using optical pumping techniques the flux of atoms in the beam turned out to be dependent on the polarisation achieved.

This dependance could be explained in the following way: First we notice that all the collisions among entirely polarized spin 1/2-particles must occur in the triplet state of the compound molecule whereas unpolarized spin-1/2-particles collide in three of four cases in the triplet state and in one case in the singlet state.

Secondly, according to the difference of the triplet- and the singlet-potential, the respective cross sectionsσ _T andσ _S are unequal. Consequently, the flux of atoms scattered from the cell into any direction must depend on the polarisation since the polarisation governs the share of singlet- and triplet-scattering in the total scattering process.