Skip to main content
6 of 6
added 116 characters in body
Cosmas Zachos
  • 66.3k
  • 6
  • 110
  • 248

First things first. You know that for the Coulomb potential there are additional invariants, the Laplace-Runge-Lenz vector beyond angular momentum, nonvanishing for elliptical orbits, classically, but vanishing for circular ones. The "lopsidedness" you are talking about amounts to the ellipse's eccentricity, a dimensionless quantity $|{\mathbf A} /me^2|$. Classically, the elliptical orbit is tantamount to angular momentum conservation in conjunction with LRL invariance.

Quantizing, classical trajectories have a very uncomfortable connection to both Wigner functions and wavefucntions. In QM, this eccentricity quantity presents as $$ \frac{\hbar \sqrt{2}}{e^2 \sqrt{m}} \sqrt{|H(L^2/\hbar^2+1)|} \qquad \leadsto \qquad \frac{\hbar \sqrt{2}}{e^2 \sqrt{m}} \sqrt{|E|( l(l+1)+1)}~~. $$

You then see this eccentricity analog never vanishes in QM, even for s waves, spherical states! This angular momentum zero-point-shift is well known in deformation quantization, and informs the proper correspondence principle, however counter-intuitive. It has been thoroughly investigated in phase space by Dahl and collaborators, J P Dahl & M Springborg, Mol Phys 47 1001 (􏰑1982)􏰀.

So, formally, the classical eccentricity survives in QM and is crucial for its spectrum. Recall it is the basis of the original modern quantization of the hydrogen atom, W Pauli Jr, "Über das Wasserstoffspektrum vom Standpunkt der neuen Quantenmechanik" Zeitschrift für Physik 36 no. 5 (1926): 336-363.

For large n, and for the largest $l=n-1$ for that n, the square root tends to 1.

Cosmas Zachos
  • 66.3k
  • 6
  • 110
  • 248