ISOTOPE SHIFTS IN THE NEAR-INFRARED LINES OF THE ARC SPECTRUM OF KRYPTON

The isotope shifts of the five even isotopes of natural krypton have been measured in 14 lines of the arc spectrum in the region 7500 to 8800 A, with precisions between 0. 04 and 0. 1 mK (1 mK equals 0. 001 cm** minus **1). The shifts are nearly proportional to mass shifts but the shifts 84-82 are approximately 0. 2 mK too small relative to those of the other even isotopes. The shift of the odd isotope 83 has been measured in five of these lines. The shifts of eight lines due to transitions of the types 5p to 5s left bracket 3/2 right bracket 2 and 5p prime to 5s prime left bracket 1/2 right bracket 1 are very similar; they are in the same sense as the Bohr shift and are between 75% and 95% greater. Six lines due to transitions of the type 5p to 5s left bracket 3/2 right bracket 2 and 5p prime to 5s prime left bracket 1/2 right bracket 0 also have nearly equal shifts; they are in the same sense as the Bohr shift but are only between 15% and 25% greater. The difference 1. 2 mK, for adjacent even isotopes, in the shifts of the two groups is due mainly to a difference in the specific mass shifts.