Hyperfine structure near infrared spectrum of atomic iodine

The hyperfine structure of spectral lines of neutral iodine (II) in the wavenumber region from 11 300 cm⁻¹ to 13 000 cm⁻¹ was studied using optical heterodyne concentration modulation absorption spectroscopy with a tunable single-mode cw Ti:Sapphire laser. The iodine atoms were produced and excited by a discharge operated in a mixture of helium and iodine vapor. A total of 89 lines were observed and the hyperfine structure of 45 of these lines was studied. For 40 lines, the hyperfine structure was not previously known. The magnetic dipole and the electric quadrupole hyperfine structure constants of 18 even and 28 odd levels were extracted. The constants of one even level and of 16 odd levels are presented for the first time. - Highlights: • Absorption spectrum of neutral iodine (II) between 11 300 cm⁻¹ and 13 000 cm⁻¹. • The hyperfine structures of II are resolved for 45 lines. • Magnetic dipole and the electric quadrupole constants are obtained. • Constants of some levels are newly reported