For 10 points, name this system containing a proton and an electron.
The Darwin term in this system's Hamiltonian corrects its energy from the effect of zitterbewegung. Lamb and Retherford demonstrated a roughly 1 gigahertz energy difference in supposedly degenerate solutions to this system. This system's wavefunction consists of a spherical harmonic multiplied by a Laguerre polynomial. The fine structure constant was first identified from the splitting in this system's spectral lines. An empirical equation modelling this system noted that its emission spectrum was quantized by the reciprocal of perfect squares. The Balmer series arises from this system according to the Rydberg equation, which models only it. This two-body system can be solved exactly by the Schrodinger equation. For 10 points, name this system containing a proton and an electron.
The Darwin term in this system's Hamiltonian corrects its energy from the effect of zitterbewegung.
hydrogen atom [or hydrogen-like atoms]