Magnetic resonance with gas-phase atoms

Abstract

Publisher Summary The magnetic resonance of gas-phase atoms suffer from both a small number of spins and low magnetic fields and the concomitant small Larmor frequencies. Special techniques like optical pumping for increasing the population difference and optical detection for sensitivity increase are required to make magnetic resonance with gas-phase atoms feasible. The technique of optical detection of magnetic resonance (ODMR), therefore, usually implies both, optical pumping and detection methods. This chapter discusses the technique in two main sections: interaction of atoms with light fields and nuclear magnetic resonance of optically polarized spins. It explains the different optical techniques used to detect the atomic sublevel coherence and to optically pump the atomic sublevels. Optical pumping is explained in the chapter as a general concept for driving the optical transitions beyond the linear regime, leading to optically induced sublevel transients and multiquantum coherences. The chapter discusses the effects of interaction of electromagnetic fields, with atoms, that causes a shift of the atomic levels and details magnetic resonance of the atomic sublevels. It also discusses the magnetic resonance of nuclear spins or rare gas atoms with no electron spin. The behavior of freely precessing nuclear spins in a rotating coordinate system and its consequence for gyroscope application as well as Berry-phase phenomena is discussed in the chapter. Gas-phase atoms are confined to a finite volume, by a container, establishing the boundary of the sample. The atoms in the sample, thus, not only interact with other gas-phase atoms but also experience the surface of the container. It is, therefore, expected that this atom–surface interaction becomes visible in the nuclear magnetic resonance properties of these atoms. A few cases have been presented in which the atom–surface interaction has been investigated in detail, with focus on the work of Stuttgart group.