9 ms·
As far as atomic physics is concerned (except for hyperfine structure), the proton is simply a blob of charge which can be to first order described by a positio
by fsh 7y ago
As far as atomic physics is concerned (except for hyperfine structure), the proton is simply a blob of charge which can be to first order described by a position-dependent charge density \rho(r). The RMS charge radius r_p is defined by r_p^2 = (\int r² \rho(r) d³r) / (\int \rho(r) d³r).
- davrosthedalek 7y agoAlmost, but not quite. The rms radius is defined via the slope of the proton electric form factor G_E. Via a Fourier transform you can connect the form factor to the distribution of charge in some space-like coordinate. That works out to be (very close) to the rest frame space for heavier atoms, because relativistic effects are small. For the proton, this is not true -- the Fourier transform gives a spacial distribution in the so called Brick-wall or Breit-frame, not in the rest frame of the proton. (There are additional complications about waveforms not being the same before and after).