Hyperfine structure of 127I2 and 129I2 optical absorption lines
Résumé
The hyperfine structure of 127I 2 and 12912 rovibronic absorption lines was investigated using either laser induced fluores-cence of a collimated molecular beam or saturated absorption in a cell. From the measurements a value for the quadrupole moment ratio 129Q/127Q = 0.699 is deduced, in good agreement with the result obtained from pure quadrupole spectra in the rf range. The study of the.hYperfine structure of 129I 2 opti-cal absorption lines is of great interest not only be-cause of its implication in laser frequency stabilization I1 ] but also because of the information on such pa-rameters as the nuclear quadrupole moment which can be deduced from a comparison with a similar study on the natural isotopic variety 127 i2" As is well known, the B ~-X transition in the iodine molecule gives rise to a very rich rovibronic absorption spectrum throughout the visible region, with a density of some five lines per cm -1 [2]. Observation of hyper-fine structure splittings, narrower than the Doppler width, calls for some kind of sub-Doppler technique. Two of them were used in the present study. The re-sults for 127I 2 were deduced from experiments on laser induced fluorescence of a collimated supersonic molecular beam, performed in collaboration with Churassy et al. [3] on the beam machine developed by them [4]. The high iodine consumption inherent to this method precludes its use with the rare weakly radioactive 129I 2 isotopic variety; the corresponding experiments were accordingly performed by the satu-rated absorption technique in a cell [5]. The same laser was used in both cases, namely a commercial R6G single frequency dye laser (Spectra Physics 580 A) * A preliminary report on this work was presented at the 6th eoUoquium on high resolution molecular spectroscopy, Tours, 1979. e~ Associated with C.N.R.S.