Dynamic polarization in a system of optically oriented atomic nuclei

David F. Zaretsky, É. A. Nersesov

Vladilen S Letokhov

Abstract A century ago Einstein introduced the notion of the linear momentum of a photon, h k, and analyzed its transfer to an atom (and back) in the establishment of thermodynamic equilibrium between black-body radiation and matter. In addition to a linear momentum, the photon also possesses an angular momentum, ħ, directed parallel (or antiparallel) to its propagation direction (the OZ axis in Fig. 4.1), depending on its polarization direction (left- or right-handed). This angular momentum is due to the spin of the photon, equal to 1. Half a century later, Kastler (1950) considered the use of the transfer of the angular momentum of a polarized photon to the angular momentum of an atom as a method of optical orientation of atoms. In essence, this was the first method to control atomic motion by means of low-intensity light, developed even before the advent of the laser; it which found widespread application in investigating and then using spin polarization effects in atomic physics. But even after lasers had made their appearance, the method of optical orientation of atoms (or pumping of certain magnetic sublevels in atoms) proved very important, specifically in the laser cooling of atoms (Chapter 5).

Gabriel E. Bene, Edmond Geneux

Patrick Bevington, R. Gartman, Witold Chałupczak

Traditionally, atomic spin orientation is achieved by the transfer of angular momentum from polarized light to an atomic system. We demonstrate the mechanism of orientation generation in room-temperature caesium vapors that combines three elements: optical pumping, nonlinear spin dynamics, and spin-exchange collisions. Through the variation of the spin-exchange relaxation rate, the transition between an aligned and an oriented atomic sample is presented. The observation is performed by monitoring the atomic radio-frequency spectra. The measurement configuration discussed paves the way to simple and robust radio-frequency atomic magnetometers that are based on a single low-power laser diode that approach the performance of multilaser pump-probe systems.

Karl H. Hausser

G. D. Cates

Over the four year period covered by this grant, we have carried out extensive research involving polarized atoms and nuclei. Using laser optical pumping, high polarizations can be produced in alkali-metal vapors. From this starting point, angular momentum can be transferred to other atoms and nuclei through several different types of spin-exchange collisions. This powerful technique enables us to study a wide variety of spin interactions and spin related phenomena. Among the systems we work with are polarized nobel gases, which display extremely long spin-relaxation times that vary from several minutes to many weeks. The use of optical pumping and spin exchange has grown enormously over the past four years.