Absolute frequency measurement of molecular iodine hyperfine transition at 534 nm

We report absolute frequency measurements of 19 hyperfine components of the rovibrational transition of molecular iodine R(53) 31-0 transitions at 534 nm with an optical frequency comb. The 534 nm laser, which is frequency-doubled from a 1068 nm external-cavity diode laser, is frequency stabilized to a hyperfine component of the I-127(2) R(53) 31-0 transition using modulation transfer spectroscopy. A frequency stability of 8 x 10(-12) at 1 s averaging time is achieved when its frequency is stabilized to the a(21) component. To obtain the absolute frequency, the pressure shift and power shift of the a(21) component are investigated. The absolute frequency of the laser locked to the a(21) hyperfine component of the R(53) 31-0 transition is measured to be 561 420 951 318 +/- 8 (type-A) +/- 12 (type-B) kHz. The observed hyperfine transitions of the iodine can be good frequency references at 534 nm and are especially useful for research on the aluminum ion optical clock, because the frequency of the iodine hyperfine transitions is dose to the second sub-harmonic frequency of the S-1(0)-P-3(1) transition of the aluminum ion at 267 nm. (C) 2019 Optical Society of America