Eur. Phys. J. D 6, 63-76 (1999)
https://doi.org/10.1007/PL00021608

Frequency measurements of hyperfine splittings in ground rovibronic states of I₂ by stimulated resonant Raman spectroscopy

¹ Laboratoire de Physique des Lasers, Université Paris-Nord, Avenue J.-B. Clément, 93430 Villetaneuse, France
² Institute of Laser Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia

Received: 26 September 1998
Revised: 30 November 1998
Published online: 15 April 1999

Abstract

Measurements of hyperfine splittings in the ground electronic state of have been performed by stimulated Raman spectroscopy. An argon laser emitting at 514.5 nm, drives the coherence between hyperfine levels of the J''=13 or J''=15 rotational levels of the ground vibronic state, via resonant excitation of the hyperfine transitions of the optical resonances (43-0) P(13) or R(15). We study the influence of the various experimental parameters on the line shape: the beam geometry, the laser modulation spectrum, the laser power, the molecular frequency shifts. We show that only beam aberrations can give rise to a significant asymmetry of the line shape, which contributes to an error in the determination of the resonance frequency. From a theoretical expression of the line shape taking into account the beam geometry, a detailed study of this error is performed. The theoretical predictions and the experimental results are in very good agreement. From the measurements, improved sets of hyperfine interaction constants for the molecule have been calculated for J''=13 and J''=15. These constants are identical for both levels, except for quadrupole coupling constant eqQ which exhibits a J-dependence, which we attribute to the centrifugal distortion of the molecule.