Probing the non-Planckian spectrum of thermal radiation in a micron-sized cavity with a spin-polarized atomic beam

Abstract

It is commonly thought that thermal photons with transverse electric polarization cannot exist in a planar metallic cavity whose size $a$ is smaller than the thermal wavelength ${\lambda }_T$, due to absence of modes with $\lambda <2a$. Computations based on a realistic model of the mirrors contradict this expectation, and show that a micron-sized metallic cavity is filled with non-resonant radiation having transverse electric polarization, following a non-Planckian spectrum, whose average density at room temperature is orders of magnitudes larger than that of a black-body. We show that the spectrum of this radiation can be measured by observing the transition rates between hyperfine ground-state sub-levels $1S_{1/2}(F,m_F)\to 1S_{1/2}(F^{\prime },m_F^{\prime })$ of D atoms passing in the gap between the mirrors of a Au cavity. Such a measurement would also shed light on a puzzle in the field of dispersion forces, regarding the sign and magnitude of the thermal Casimir force. Recent experiments with Au surfaces led to contradictory results, whose interpretation is much controversial.

arXiv comment11 pages, 9 figures. Accepted for publication in Phys. Rev. A

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Cited by in corpus (2)

• Blackbody thermodynamics in the presence of Casimir's effect
• Casimir-Polder shift of ground-state hyperfine Zeeman sub-levels of hydrogen isotopes in a micron-sized metallic cavity at finite temperature