Amazing stuff!
"... Now, physicists have observed such tiny impacts by detecting individual atoms in a gas colliding with a tiny glass sphere, or nanoparticle, suspended in laser light. The technique ... could potentially lead to a new standard for defining pressure, push the limits of quantum theory, and help scientists search for new particles. ...
Such a system could also be used to develop a new standard to define pressure in an ultrahigh vacuum, just as an atomic clock defines the second. Researchers could determine the pressure by counting collisions ..."
From the abstract:
"We experimentally demonstrate the detection of momentum transfers from individual collisions of Kr, Xe, and SF6 with an optically levitated nanoparticle, finding good agreement with theoretical expectations.
The observed event rates accurately measure the gas partial pressures, while the spectral shape provides a sensitive probe of the surface properties of the nanoparticle, including its temperature.
The reconstruction of impulse signals as small as 200 keV/c further establishes that levitated optomechanical sensors can reach the sensitivity required for precision measurements of fundamental particle interactions, and demonstrates a proof-of-principle for a primary pressure sensor based on the detection of individual gas particle collisions."
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