From optical pumping to quantum gases

Pierre-Jean Nacher

George William Series

This article traces the development of optical pumping from the ideas first elaborated by Kastler in 1950. It deals with the general characteristics of optical pumping, the optical ‘magnetization’ of gases and vapours, spin exchange, metastability exchange, orientation by collision, multiple quantum resonances, atomic coherences, quantum beats, and dressed atoms: and concludes with a note on laser spectroscopy.

Claude N. Cohen-Tannoudji

Thad G Walker, W. Happer

Spin-exchange optical pumping of mixtures of alkali-metal vapors and noble gases can be used to efficiently polarize the nuclei of the noble-gas atoms. Liters of noble gases at standard temperature and pressure and with nuclear spin polarizations of several tens of percent are now used in many applications. The authors describe the basic phenomena that govern the spin-exchange process and review the physics of angular momentum transfer and loss in optical pumping and spin-exchange collisions.

T. Yabuzaki, Toru Ogawa

Marziale Milani, Guido Baroni, Lorenzo Ferraro +3 more

Recently the demand for hyperpolarized noble gases is arising to improve NMR spectroscopy resolution for imaging. Hyperpolarization of noble gases is achieved by spin- exchange with alkali metal. atoms that undergo optical pumping by circularly polarized radiation. Optical pumping is usually achieved by high power semiconductor lasers. These sources have a bandwidth very large when compared with the transition bandwidth of the optically active species. This has two serious consequences: (i) the request of high power lasers, (ii) the losses that the unemployed energy delivered to the Rb vapor can provide in the efficiency of the energy transfer. Object of our investigation will be the comparison of two experimental set ups for optical pumping of Rb vapor where pumping is given in one case by a dye laser pumped by a UV nitrogen laser built in our laboratory according to the Blumlein scheme and in the other case by a semiconductor laser. Major elements that will be discussed are (1) the role of stimulated emission of Rb vapor to increase the pumping efficiency, (2) the fate of resonant photons that are emitted during Rb decays, (3) the role of applied magnetic fields in the efficiency of pumping processes.