Absolute frequency measurements and hyperfine structures of the   molecular iodine transitions at 578 nm
  We report absolute frequency measurements of 81 hyperfine components of the rovibrational transitions of molecular iodine at 578 nm using the second harmonic generation of an 1156-nm external-cavity diode laser and a fiber-based optical frequency comb. The relative uncertainties of the measured absolute frequencies are typically $1.4\times10^{-11}$. Accurate hyperfine constants of four rovibrational transitions are obtained by fitting the measured hyperfine splittings to a four-term effective Hamiltonian including the electric quadrupole, spin-rotation, tensor spin-spin, and scalar spin-spin interactions. The observed transitions can be good frequency references at 578 nm, and are especially useful for research using atomic ytterbium since the transitions are close to the $^{1}S_{0}-^{3}P_{0}$ clock transition of ytterbium. 
Takumi Kobayashi, Daisuke Akamatsu, Kazumoto Hosaka, Hajime Inaba, Sho   Okubo, Takehiko Tanabe, Masami Yasuda, Atsushi Onae...
physics.atom-ph physics.optics