Phys. Rev. Lett. Phys. Rev. A Phys. Rev. B Phys. Rev. C Phys. Rev. D Phys. Rev. E Phys. Rev. ST AB Rev. Mod. Phys. Phys. Rev. (Series I) Phys. Rev. Volume: Page/Article:

Phys. Rev. B 32, 6374–6384 (1985)

[Issue 10 – 15 November 1985 ]

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Grazing-incidence antireflection films. IV. Application to Mössbauer filtering of synchrotron radiation

J. P. Hannon and G. T. Trammell

Physics Department, Rice University, Houston, Texas 77251

M. Mueller, E. Gerdau, R. Rüffer, and H. Winkler

II. Institute für Experimentalphysik, Universitat D-2000 Hamburg 50, Federal Republic of Germany

In principle, a very bright, monochromatic 1-A-ring signal with [h-bar] Delta omega [approx equals] 10^-8–10^-6 eV can be filtered from white synchrotron radiation by multiple reflection at grazing incidence from mirrors coated with grazing-incidence antireflection (GIAR) films in which either the films or substrate contain resonant Mössbauer nuclei. Typically, nonresonant reflectivities can be suppressed to 10^-4–10^-3 while maintaining resonant reflectivities of [approx equals] 70%, with half-widths strongly broadened by ``enhancement'' to Gamma _{eff [approx equals] 20 Gamma} . Effective filtering should be possible with two to four reflections, or alternatively, with one to two reflections plus time resolution.

By using different combinations of films and substrates, the response can be tailored to give narrow resonance widths Delta omega [approx equals] Gamma and corresponding delayed scattering times to optimize time filtering, or at the other extreme, to produce broad-width filters with [h-bar] Delta omega [approx equals] 100 Gamma which would be ideal for a high-resolution x-ray source. In the time response there will be ``quantum beats'' at frequencies Omega <sub>B</sub> due to the interference between the radiation emitted by different hyperfine oscillators, so the beat pattern is determined by the hyperfine splitting. Also, there are two interesting dynamical effects—first, due to the ``enchancement effect'' the coherent decay is speeded up relative to the natural lifetime for incoherent decay and internal conversion absorption; and secondly, there will be ``dynamical beats'' at frequencies omega <sub>B</sub> (superimposed on the quantum-beat spectrum) which is essentially an interference between the natural ``ringing'' of an oscillator at its resonsance frequency omega ₀ and the collective response which rings with a median frequency omega ₀+ omega _B.

Finally, there is also a multiple-reflection delay to the response, which should be a useful aid for time filtering. This paper develops the general theory for resonant filtering of synchrotron radiation using GIAR films, examining in particular the resulting frequency spectrum, the integrated response, and the time response for resonant ⁵⁷Fe mirrors coated with lambda /4 GIAR films.

©1985 The American Physical Society

URL: http://link.aps.org/abstract/PRB/v32/p6374
DOI: 10.1103/PhysRevB.32.6374
PACS: 78.65.-s, 76.80.+y, 42.78.Hk

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References

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