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Physical Review A

Level-Crossing Signals in Stepwise Fluorescence

R. Lowell Smith, T. G. Eck

Published Dec 1, 1970• 22 citations
Publisher

Abstract

A discussion is given of the requirements for observing strong level-crossing signals in stepwise fluorescence, where the state under investigation is optically excited via an intermediate state, the atom absorbing in the process two photons of different wavelengths. Data obtained using this technique are presented for fine-structure crossings in the ${3}^{2}D$ term of Li.

DOI
10.1103/physreva.2.2179

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Experimental Study of the Fluorescence Spectrum Emitted by Two-Level Atoms under Strong Bichromatic Excitation

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Springer eBooks•Jan 1, 1989•2 citations
A discussion is given of the requirements for observing strong level-crossing signals in stepwise fluorescence, where the state under investigation is optically excited via an intermediate state, the atom absorbing in the process two photons of different wavelengths. Data obtained using this technique are presented for fine-structure crossings in the 32D{3}^{2}D32D term of Li.
The level-crossing technique of atomic spectroscopy utilizes the spatial interference in the scattering of resonance radiation which can occur when two Zeeman levels of an atom are brought into coincidence ("crossed") by the application of an external magnetic field. "Anticrossing" refers to the case where the two levels involved are coupled by a small static interaction. In this paper the general expression for an anticrossing signal is given and its predictions compared with signals observed in the 22P2 ^{2}P22P term of Li. It is shown that anticrossings produce signals in many experimental situations for which there would be no signal from a normal level crossing.
Inelastic-collision processes in fine-structure-changing collisions have been studied by selective stepwise excitation and observation of the resulting fluorescence. Hereby, the effect of ground-state rubidium atoms colliding with excited-state rubidium atoms was investigated. The ground-state density was changed by three orders of magnitude by performing the measurements over the temperature range of 75 to 200 \ifmmode^\circ\else\textdegree\fi{}C. The cross section for fine-structure-changing collisions [i.e., $\mathrm{Rb}({6}^{2}{D}_{\frac{5}{2}})+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{Rb}({6}^{2}{D}_{\frac{3}{2}})+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})$] is ${\ensuremath{\sigma}}_{\mathrm{fs}}=(1.0\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ cm2{\mathrm{cm}}^{2}cm2. The cross sections for transfer out of the fine-structure doublet [i.e., $\mathrm{Rb}({6}^{2}D)+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{states}\mathrm{other}\mathrm{than}\mathrm{Rb}({6}^{2}D)$] is ${\ensuremath{\sigma}}_{\mathrm{tr}}=(3.8\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ cm2{\mathrm{cm}}^{2}cm2. It is demonstrated that for the intermediate excited rubidium states, both the fine-structure-changing and transfer cross sections are of the order of the geometrical cross section of the excited rubidium states.