Search for deviations from the ideal Maxwell-Boltzmann distribution for a gas at an interface

Abstract

The isotropic Maxwell-Boltzmann (M-B) velocity distribution is the accepted standard for a gas at thermal equilibrium, with the Doppler width considered to deliver a very precise measurement of the temperature. Nevertheless, the physical nature of the surface, and the atom-surface interaction, in its long-range (van der Waals type) regime as well as in its short-range regime leading to adsorption/desorption mechanisms, are far from the ideal situation describing the foundation of gas kinetics. Through the development of vapor spectroscopy at an interface, a high sensitivity to atoms flying nearly parallel to the gas interface is obtained, and deviations to M-B distribution could have observable effects, even affecting the ultimate limits to resolution. We report here on the development of an experiment involving a dedicated set-up of spatially-separated pump-probe experiment in a narrow cell. A first series of investigation could not evidence a deviation for Cs atom velocities at a nearly grazing incidence (typically 1.5 -5°). We discuss various technical improvements to increase the sensitivity to atoms flying parallel to the surface, along with specific spectroscopic information that may be collected. Alternately, the comparison of standard selective reflection spectroscopy with simultaneous volume spectroscopy may be a source of complementary information. At last, we discuss how the Boltzmann energy distribution, among molecular or atomic levels, may become sensitive to specific thermal exchanges at the surface, in an equilibrium situation.

arXiv commentTo appear as "Invited" in SPIE Proceedings of 20th ICSQE (International Conference and School on Quantum Electronics) Nessebar, Bulgaria, Sept 17-21, 2018

References in corpus (7)

• Ballistic molecular transport through two-dimensional channels
• First direct determination of the Boltzmann constant by an optical method
• Exploring the van der Waals Atom-Surface attraction in the nanometric range
• Casimir-Polder forces in the presence of thermally excited surface modes
• Selective Reflection Spectroscopy at the Interface between a Calcium Fluoride Window and Cs Vapour
• Testing the limits of the Maxwell distribution of velocities for atoms flying nearly parallel to the walls of a thin cell
• Detection of slow atoms confined in a Cesium vapor cell by spatially separated pump and probe laser beams

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• Spectrally Sharp Near-Field Thermal Emission: Revealing Some Disagreements between a Casimir-Polder Sensor and Predictions from Far-Field Emittance
• New probability distributions in astrophysics: III. The truncated Maxwell-Boltzmann distribution