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Relaxation experiments have been performed between 0–200 G on optically polarized Rb atoms in argon, krypton or xenon, at pressures ranging from 0.1 to 20 torr. They clearly show the existence of Rb–Ar, Rb–Kr and Rb–Xe molecules of low binding energy (smaller than kT). Molecular parameters such as lifetime, spin-orbit coupling constant, formation rate, constant of mass action, etc., are measured, or evaluated when they cannot be directly measured. Experimental values of the diffusion coefficient of Rb in the gas (except xenon) and of the disorientation cross sections by usual binary collisions are also obtained.

We propose a novel approach of photoreflectance microscopy that provides a direct visualization of the phase contour lines of the thermal wave. The method is applicable to (possibly heterogeneous) samples of mediocre polish. In a locally homogeneous region it yields the local thermal diffusivity.

Résumé. 2014 Nous présentons des mesures par effet Hanle de la relaxation dans l'état 7 S1/2 du césium induite par collisions avec des atomes de césium ou des atomes de gaz tampon (hélium), en présence d'un champ électrique. Les résultats montrent que la relaxation de la polarisation électronique reste isotrope dans la configuration adoptée et justifient le procédé de calibration utilisé dans nos récentes mesures de violation de la parité sur la transition 6 S-7 S du césium. Nous obtenons aussi la durée de vie de l'état 7 S1/2 : 03C47S = 48,5 ± 0,5 ns (et la section efficace de dépolarisation 03C3CsHe = (1,10 ± 0,05) x 10-15 cm2). Par suite la valeur semi-empirique de la polarisabilité scalaire de la transition 6 S-7 S devient 03B1 = -(265,1 ± 2,5) a30. Abstract 2014 We report Hanle effect measurements of the relaxation in the 7 S1/2 state of cesium by collisions with cesium or buffer gas (helium) atoms in an electric field. The results show the relaxation of the spin polarization to remain isotropic in the adopted configuration, and justify the calibration procedure used in our recent measurements of parity violation in the 6 S-7 S transition of cesium.We also obtain the lifetime of the 7 S1/2 state : 03C47 S = 48.5 ± 0.5 ns (and the depolarization crosssection 03C3CsHe = (1.10 ± 0.05) x 10-15 cm2). Accordingly the semi-empirical value of the scalar polarizability of the 6 S-7 S transition becomes 03B1 = -(265.1 ± 2.5) a30.

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