D. W. Goodwin's Advances in Quantum Electronics. Volume 3 PDF

By D. W. Goodwin

ISBN-10: 0120350033

ISBN-13: 9780120350032

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BALLING D . SPIN-EXCHANGE COLLISIONS In a typical spin-exchange optical-pumping experiment, alkali atoms are polarized by optical pumping, and free electrons or another species of atom or ion are polarized by spin-exchange collisions with the optically-pumped alkali atoms. In order to understand the optical-pumping signals, we must determine how the spin systems of the two sets of particles are coupled by spin-exchange collisions. T o do this, we must calculate the effect of these collisions on the density matrices of the two spin systems.

For simplicity we will first consider a situation where we are interested in one observable A only. The eigenvalues of A are ai, and we will assume for the moment that the spectrum is discrete. That is, A\a,,ty = a¿a,,ty. 3) Although we cannot write down the state vector of a particular atom in our ensemble, we may be able to say what the probability is of finding an atom in the OPTICAL PUMPING 31 State | ú f ¿ , / > . If this probabiUty is Piai), then the average of a large number of measurements of the observable A is just

If we introduce the abbreviations Ai = [cko - cki + k i . 16) é , . 18) and ifij^h^UO = <μ + l l ^ + l μ>Aik^e'^'a,(t). 19) In order to integrate these equations we require the initial conditions at / = 0. We will assume that the atom is initially in its ground state so that BMM = 0. 21) the standard assumption in Ist-order perturbation theory. 26) If the Zeeman splittings in the ground state and excited state of the atom are small compared with the energy separation of the excited and ground states chko, we can neglect the Zeeman energy in (A.

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Advances in Quantum Electronics. Volume 3 by D. W. Goodwin


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