Narrow lines in molecular iodine near the dissociation limit

The experimental set-up for high-resolution spectroscopy of iodine at 501.7 nm, near the dissociation limit, is described. Line shapes of about 30 kHz wide are obtained with hyperfine components of the R(26)62-0 transition. Preliminary results on the absolute frequency measurements of the Ar
⁺
laser locked onto these transitions are given.