We report the detection of individual nuclear $α$ decays through the mechanical recoil of the entire micron-sized particle in which the decaying nuclei are embedded. Momentum conservation ensures that such measurements are sensitive to any particles emitted in the decay, including neutral particles that may otherwise evade detection with existing techniques. Detection of the minuscule recoil of an object more than $10^{12}$ times more massive than the emitted particles is made possible by recently developed techniques in levitated optomechanics, which enable high-precision optical control and measurement of the mechanical motion of optically trapped particles. Observation of a change in the net charge of the particle coincident with the recoil allows decays to be identified with background levels at the micro-Becquerel level. The techniques developed here may find use in fields ranging from nuclear forensics to dark matter and neutrino physics.
  • Lvxferre@mander.xyz
    ·
    9 months ago

    Some Erwin guy told me that the first step is to find a cat.

    Jokes aside, the strategy seems elegant, even given the physical restrictions mentioned in the intro.

    First, almost all charge changes are measured to be in the positive direction—i.e., the spheres nearly always lose more electrons than protons for both the α and β decays in the decay chain

    This is bugging me a bit - why would α decay increase the charge? Since you're expelling a positively charged particle, I'd expect a decrease; and if the α particles are trapped on the silica, or steal electrons from it, you'd expect no change in charge. Perhaps the rest of the article mentions the reason (I'm still digging through it).

    • Salamander@mander.xyzM
      ·
      9 months ago

      This is bugging me a bit - why would α decay increase the charge?

      What is changing is the net charge, which refers to an excess of negative or positive charge. A neutral atom has the same number of protons as it does electrons, and so its net charge is 0. In a decay process an atom will emit, create, and/or annihilate different types of particles directly as part of the decay event, and immediately after the decay there can also be ionization events in which the excited daughter atom and even atoms around it can eject electrons (for example, via the Auger effect, emission of secondary electrons via impact ionization, and other processess).