The frequencies of three Doppler-free absorption lines of the <sup>127</sup>I<sub>2</sub> molecule in the vicinity of 730 nm have been measured interferometrically with reference to an iodine-stabilized 633-nm He–Ne laser. These frequencies are important as transfer standards for Doppler-free, two-photon spectroscopy of the 1S–2S transitions in muonium, hydrogen, and deuterium (with the use of frequency tripling to generate the necessary 244-nm radiation). The a<sub>15</sub> component of the R(26) 5–13 transition has recently been used as a reference line in a high-precision measurement of the muonium 1S–2S frequency interval. Under the conditions reported, the frequency of this transition was found to be 409 253 981.70 (0.14) MHz, ~680 MHz away from the muonium transition.
© 2000 Optical Society of America
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.3940) Instrumentation, measurement, and metrology : Metrology
(300.6320) Spectroscopy : Spectroscopy, high-resolution
(300.6390) Spectroscopy : Spectroscopy, molecular
S. L. Cornish, Yi-Wei Liu, I. C. Lane, P. E. G. Baird, G. P. Barwood, P. Taylor, and W. R. C. Rowley, "Interferometric measurements of 127I2 reference frequencies for 1S–2S spectroscopy in muonium, hydrogen, and deuterium," J. Opt. Soc. Am. B 17, 6-10 (2000)