Rotation dependence of

Frequency-stabilized lasers are of considerable interest not only for the implementation of time and length standards but also as tools to study atoms and molecules. The absolute frequencies and hyperfine structures of the R(38)44-0, P(36)44-0, R(37)44-0, P(35)44-0, R(36)44-0, P(34)44-0, and R(58)45-0 lines of molecular iodine (127I2) at 514 nm were measured in this study via modulation transfer spectroscopy. The hyperfine splittings were fitted to a four-term Hamiltonian with an uncertainty of approximately 1 kHz to obtain high-precision hyperfine constants. The rotation dependence of the excited-state (B state, v′ = 44) hyperfine constants was determined using the fitted hyperfine constants. Notably, 103 hyperfine transitions were observed, with an uncertainty of 5.6 kHz (a fractional uncertainty of 9.6 × 10–12), thereby providing new optical frequency references for telecommunication and other applications