Measurement of Iodine Purity in Absorption Cells for Laser Frequency Stabilization

In the contribution we present a system for measurement of iodine purity by means excitation of a selected strong transition, measurement of induced fluorescence and evaluation by the Stern-Volmer formula. The arrangement is based on a pumping Ar-ion laser tuned to the transition of interest but its linewidth far exceeds the transition. Frequency noise of the laser is effectively reduced by monitoring the fluorescence in a second, reference iodine cell and together with monitoring of the laser power enables cancellation of the frequency noise influence which generates errors by demodulating on the absorption profile. The level of the scattered light is subtracted as well. All the measured data are digitally processed and the experiment is fully computer controlled.