摘要
We report absolute frequency measurement of the molecular iodine P(28) 24-0 a 1 , a 10 , and a 15 hyperfine transitions at 548 nm. The light source is based on a frequency-doubled fiber amplifier system seeded by an external cavity diode laser. Saturated absorption is performed by modulation transfer spectroscopy, and the absolute transition frequency is measured by an optical frequency comb. The effects of pressure shift and pressure broadening are discussed. Our determination of the line centers reaches a precision of better than 20 kHz. This light source can be used as a reference laser for lithium ion spectroscopy. © 2013 Optical Society of America.