Isotope Shift In Neutral Oxygen*†

Abstract

An O18-enriched oxygen sample (donated by A. O. Nier) has allowed examination of isotope structure in 20 atomic lines between 2000 and 11 000A. Strong sharp lines were obtained in a liquid nitrogen-cooled electrodeless quartz discharge tube containing up to 0.5 mm of oxygen in 5 mm of helium excited by a 10 mc oscillator. The discharge was photographed through an external Fabry-Perot interferometer in series with a large prism spectrograph. The shifts found ranged from zero to as high as 0.5 cm−1 for λ4233 (4p3P–3d′3P) and λ2884 (3p3P–3d′3P). Enough data was available to allow a study of the internal consistency of the measured shifts as a test of the mass-effect theory. With the measured shifts in two lines, two theoretical parameters for the specific effect were empirically determined and used to predict shifts in several other lines. It is concluded that the mass-effect theory is generally applicable to oxygen and that the abnormally large shifts found for λ4233 and λ2884 are the result of interactions affecting the common upper level. A comparison is made with earlier nitrogen data. Use is made of the formal relationship of specific effect parameters to certain radiation theory integrals in calculating a transition probability and an f value for the λ1306 resonance triplet. The reasonable values obtained are a further indication of the validity of the theory.