FREQUENCY SHIFTS IN SPIN-EXCHANGE OPTICAL PUMPING EXPERIMENTS
>A theory is derived to predict the density matrices describing two atoms after a spin-exchange collision from the density matrices before the collision and the scattering amplitude for binary collisions. This theory is then applied to a system of quasifree electrons interacting with optically, pumped rubidium atoms. For calculating the change in the electron density matrix, the Rb/sup 85/ and Rb/sup 87/ are replaced by a fictitious rubidium isotope with no nuclear spin. Expressions are derived for the change in the light transmission when a radio-frequency field is present at the electron frequency. In addition to the linewidth for the electron signal, the spin- exchange theory predicts a frequency shift the magnitude of which depends upon the two-body scattering amplitude, the rubidium polarization, and the rubidium density. Experiments performed to test various aspects of the theory are reported. The measurements were made on a system of quasifree electrons interacting with rubidium atoms. Measurements of the electron linewidth as a function of temperature indicated that spin-exchange collisions dominated the electron relaxation. The predicted frequency shift was measured by observing the electron resonance frequency first with left circularly polarized light and then with right circularly polarized light. For electrons colliding with rubidium atoms the shift is negative when the rubidium polarization is positive and the ratio of the shift to the linewidth is delta nu /sub O// DELTA nu = -0.025 plus or minus 0.005. From the measured values of the shift and the linewidth, a value is derived for the electron-rubidium spin-flip cross section. The replacement of Rb/sup 86/ and Rb/sup 87/ by the fictitious rubidium isotope with no nuclear spin is justified. The calculations for the simple electron-rubidium system are generalized and applied to more complicated systems. Results are reported for the change in the density matrix of hydrogen atoms when they collide with polarized electrons, the change in the density matrix of Rb/sup 87/ atoms when they collide with polarized electrons, and the change in the density matrix of hydrogen atoms when they collide with hydrogen atoms. (auth)
- Research Organization:
- Harvard Univ., Cambridge, Mass.
- NSA Number:
- NSA-18-007773
- OSTI ID:
- 4108126
- Journal Information:
- Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Vol. Vol: 133; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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