Optical pumping of atoms

In the analysis of optical pumping of atoms, when the values of the quantum numbers J", J and J" are, as a rule, of the order of unity, and hence the number of magnetic sublevels is small, the system of equations... 

Auzinsh, M.P. (1992). Dynamic Stark effect action on optical pumping of atoms in an external magnetic field, Phys. Lett. A, 169, 463—468. 

Duclqy, M. (1973). Nonlinear effects in optical pumping of atoms by a high intensity multimode gas laser. General theory, Phys. Rev. A, 8, 1844-1859. 

If the ojjtical field that excites atoms or molecules is strong enough, it can create Zeeman coherences not only in the excited state of atoms or molecules, but also in the ground state. In a slightly different context this effect for the first time was studied as an optical pumping of atomic states. 

Ducloy, M., Nonlinear Effec ts in Optical Pumping of Atoms by a High-Intensity Multimode Gas Laser. Genaral Theory. Phys. Rev. A, 8 (4) p. 1844 - 1859, (1973). Auzinsli, M.P. and R.S. Ferber, Optical-Pumping of Diatomic Molecules in the Electronic Ground State — Classical and Quantum Approaches. Phvs. Rev. A, 43 (5) p. 2374 - 2386, (1991). 

While optical pumping of atoms generally requires tunable lasers, most of the experiments on moleoules up to now have been performed with fixed frequency lasers (e.g., the He-Ne or argon and krypton laser lines). Because most molecules have such dense absorption spectra with numerous lines corresponding to transitions (v",J ) - (v, J ) between a lower vibrational-rotational level (v",J ) and an upper level (v, J ) there is nearly always a fortuitous overlap between a fixed laser line and one or even several molecular lines within a molecular absorption band. The number of molecular transitions excited simultaneously depends on the line density and on the laser linewidth (see Fig.8.24). 

D Laser Optical Pumping of a Sodium-atom Beam 365... 

Generally speaking, the influence of fly-through effects on the optical pumping of the lower level is essential for various non-linear phenomena [268]. These problems, on application to atomic systems, are treated, for instance, in [10]. 

The system of equations obtained, (5.22) and (5.23), in broad line approximation in many cases allows us to carry out the analysis of non-linear optical pumping of both atoms and molecules in an external magnetic field. Some examples will be considered in Section 5.5, among them the comparatively unexplored problem of transition from alignment to orientation under the influence of the dynamic Stark effect. But before that we will return to the weak excitation and present, as examples, some cases of the simultaneous application of density matrix equations (5.7) and expansion over state multipoles (5.20). 

It is worth noting that the four-fold symmetry of hexadecapole moment is revealed only at the synchronous pumping and, what is important, at time moments when the hexadecapole moment is precisely aligned with one of its symmetry axis along the linear polarization of the field and the atomic coherence p 2, 2 in the M-system has its maximal value. The periodic change of the optical properties of atomic medium modulates the angle of tight polarization that leads to the FM NMOR resonances. If the time-dependent optical rotation is measured at the first harmonic of (.lm, a resonance is seen when Qm = k Ql which allows one to separate the NFS produced by different atomic PM. Indeed, in the experiment the in-phase and quadrature amplitudes of optical rotation,... 

The second scheme is based on the state-selective reionization of the optically pumped neutral atomic beam, followed by ion counting [66]. The method has been used successfully to study long isotopic chains of the noble gases Ar [67],, 6Kr... 

The combination of collinear fast-beam laser spectroscopy and P-RADOP (radiation-detected optical pumping) has been used to measure nuclear spins and moments of neutron-rich isotopes of the light alkali elements jLi [72-74] and Na [75]. Here, the optically pumped fast atomic beam is implanted into a single crystal placed in a static magnetic field. The NMR signal is destroying the nuclear polarization detected by measuring the p-decay asymmetry. 

Fig. 5.5 Level scheme for nuclear spin polarization by optical pumping of the Na atom with nuclear spin i = h...

Although the recoil effect is very small when a single photon is absorbed, it can be used effectively for optical cooling of atoms by the cumulative effect of many absorbed photons. This can be seen as follows When atom A stays for the time T in a laser field that is in resonance with the transition j) ), the atom may absorb and emit a photon tko many times, provided the optical pumping cycle is short compared to T and the atom behaves like a true two-level system. This means that the emission of fluorescence photons fuo by the excited atom in level k) brings the atom back only to the initial state i), but never to other levels. With the saturation parameter S = Bikp (Oik)/Aik, the fraction of excited atoms becomes... 

V. Diemer, W. Demtrdder, Infrared atomic Cs laser based on optical pumping of Cs2 molecules. Chem. Phys. Lett. 176, 135 (1991)... 

The first ideas about the control of atoms by light (for the case of the orientation of atoms) were born even before the advent of the laser. I have in mind the fundamental work by Kastler on the optical control of the orientation of atoms produced by optical pumping (Kastler 1950). This work had an effect not only on the development of the laser, but also on the use of the laser light for the cooling of atoms. I have therefore considered it necessary to treat the optical orientation of atoms. 

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