The hyperfine structure separations of about 25 terms of T1 II have been measured by means of two quartz and two glass Lummer plates used in conjunction with a Hilger E1 spectrograph. The light source was a hollow cathode discharge in helium. Large isotope displacements have been found in some of the terms of the 5d96s26p configuration, also in the 6p2 3P2 and 6p2 1D2 terms. The results have been used to calculate g(I) and to examine the validity of the application of the summation rules to the separation factors for the 6snd and 6snf configurations. The spacing of the system of levels arising from the 6s6f configuration has been examined.
Hyperfine structure of molecular iodine measured using a light source with a laser linewidth at the megahertz level
