The isotope shifts of the five stable even isotopes of krypton have been measured in six lines of Kr i in the region 4270–4500 Å, with precisions between 0.06 and 0.1 mK (1 mK = 0.001 cm1). Three of these lines are due to transitions 5s[3/2]2–6p and the other three to transitions 5s[3/2]1–6p.The shifts are in the same sense as the Bohr shift and are (for the pair 86-84), respectively, 0.4 and 1.5 mK greater; they are nearly proportional to mass shifts but show divergences similar to those found in the lines 5570 and 5562 Å (Brechignac and Champeau and Keller), and in 14 infrared lines (Jackson). King diagrams show that the field shifts of the lines of the two groups 5s[3/2]2–6p and 5s[3/2]1–6p are approximately equal and are rather greater than those of the lines 5570 and 5562 Å and the 14 infrared lines. The isotope shifts in the lines 5870 Å (5s[3/2]1–5p′[3/2]2) and 6456 Å (5p[5/2]3–6d[7/2]4) have also been measured; the field shifts of the former are approximately equal to those of the green and infrared lines referred to above while those of the red line are smaller. Approximate values (precision 0.4 mK) have been found for the isotope shift 86-83 in the three lines with transitions 5s[3/2]1–6p. An analysis of the differences of the mass shifts and the ratios of the field shifts of 24 lines in the near infrared and visible regions shows that the field shifts are probably small (0.3 or 0.4 mK for 86-84) and are in the same sense as the Bohr shift; they are not proportional to the change in mass number.
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