Abstract
A compact device (lengh 175 mm) has been built for the energy resolved detection of low energy (1–5 eV) Penning electrons with a 2π solid angle collection efficiency, based on the principle of adiabatic parallelisation of electron motion in a diverging magnetic field. A retarding field analysis is then used as a high pass filter to discriminate between Penning electrons released in collisions of rare gas atoms in metastable and shortlived, laser excited states. The overall detection efficiency is 0.13. The Zeeman-splitting of the atomic levels in the scattering center (maximum B = 222 G) allows the preparation of single magnetic substates | J, M⪢ B . By rotating the detector in the collision plane, well defined | J, M⪢ g states can be produced with respect to the relative velocity g, the quantization axis relevant for the collisions. The system has been tested by measuring the collision energy dependence of polarized-atom cross sections J Q | M| for the Ne* [ 3P 2]-Ar and Ne** [ 3D 3]-Ar systems. For the Ne* [ 3P 2] metastable atoms we find 2 Q 0/ 2 Q 2 = 1.55 ± 0.06 and 1.05 ± 0.06 in the thermal and superthermal energy range, respectively, which should be compared to 1.30 of Bregel et al. at thermal energies. For the Ne** [ 3D 3] state we find 3 Q 0,1/ 3 Q 2,3 = 1.65 ± 0.06 and 1.00 ± 0.10 for the same energy ranges.
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