Doppler-free high-resolution spectroscopy is applied to molecular iodine at 532 nm by Nd:YAG lasers. The main hyperfine components as well as the crossover lines are measured for R(56)32–0 and P(54)32–0 transitions by heterodyne beating of two I<sub>2</sub>-stabilized lasers. The measured hyperfine splittings including both main and crossover lines are fitted to a four-term Hamiltonian, which includes the electric quadrupole, spin–rotation, tensor spin–spin, and scalar spin–spin interactions, with an average deviation of ∼1 kHz. Absolute values of the electric quadrupole hyperfine constants for both the upper and the lower states are obtained. The rotation dependence of the ground-state (v<sup>″</sup>=0) electric quadrupole constant eQq<sup>″</sup> is found to be eQq<sup>″</sup>(J)=−2452.556(2)−0.000164(5)J(J+1)−0.000000005(2)J<sup>2</sup>(J+1)<sup>2</sup> MHz.
© 2001 Optical Society of America
(020.2930) Atomic and molecular physics : Hyperfine structure
(120.3940) Instrumentation, measurement, and metrology : Metrology
(300.6320) Spectroscopy : Spectroscopy, high-resolution
(300.6390) Spectroscopy : Spectroscopy, molecular
(300.6460) Spectroscopy : Spectroscopy, saturation
Feng-Lei Hong, Jun Ye, Long-Sheng Ma, Susanne Picard, Christian J. Bordé, and John L. Hall, "Rotation dependence of electric quadrupole hyperfine interaction in the ground state of molecular iodine by high-resolution laser spectroscopy," J. Opt. Soc. Am. B 18, 379-387 (2001)