Hyperfeinstrukturuntersuchungen mit einem sphärischen Fabry-Perot-Interferometer mit internem Absorptionsatomstrahl im Tm I- und Eu I-Spektrum

A spherical Fabry-Perot spectrometer with an absorbing atomic beam passing the interior of the interferometer is described. By use of the internal beam it is possible to reduce the amount of material needed for the atomic beam source to a few milligrams per hour. The set-up is especially suitable for hyperfine structure and isotope shift investigations. For the photoelectric recording of the signal the geometrical distance between the spherical mirrors was changed using the piezoelectric effect. In order to reduce the influence of the intensity distribution of the light sourceI ₀(λ) the ratio I ₀(λ)-I(λ)]/I ₀(λ) was measured, whereI ₀(λ)=I ₀(λ) exp (—V·k(λ)·d) is the observed intensity with absorbing atoms between the mirrors, andV the increase of the absorption signal due to the multiple reflections of the light through the atomic beam (V≈75). For an accurate and easy evaluation of the data this ratio was measured by a digital voltmeter and punched into paper tape. The small line width of the absorption profile obtained in the experiments with Tm and Eu enabled us to measure hyperfine distances of the order of 5 · 10^?3 cm^?1 to 20 · 10^?3 cm^?1 with an error not exceeding 0.1 · 10^?3 cm^?1 in some cases. From the measurements theA-factors for five levels of the configurations 4f ¹³6s 6p and 4f ¹²5d 6s ² in Tm I and theA- andB-factors of the stable Eu isotopes of the 4f ⁷ 6s 6p y ⁸ P _5/2level in Eu I were determined.