An electron of reduced mass is bound to a nucleus of charge by the Coulomb potential

PHYSICS · Subjective · Fermi University Physics · Quantum Mechanics · Symmetry, angular momentum and spin · Central potentials and canonical three-dimensional systems

The Structure of Quantum Mechanics, Ch Central potentials as a rotation problem

Problem

An electron of reduced mass μ\mu is bound to a nucleus of charge +Ze+Ze by the Coulomb potential V(r)=−Ze24πϵ0rV(r) = -\dfrac{Ze^2}{4\pi\epsilon_0 r}, with no other interaction present. (a) Show that [H^,L⃗^]=0[\hat H,\hat{\vec L}] = 0, and explain why this forces every energy eigenspace of H^\hat H to decompose into a direct sum of (2l+1)(2l+1)-dimensional multiplets. (b) Restricting H^\hat H to one such multiplet, obtain the equation satisfied by the reduced radial function u(r)=rR(r)u(r) = rR(r), using the symmetric radial momentum p^r=−iℏ(∂r+1/r)\hat p_r=-i\hbar(\partial_r+1/r) (not the naive −iℏ∂r-i\hbar\partial_r), and give Veff(r)V_{\rm eff}(r) explicitly for this potential. (c) Derive, rather than assume, the boundary condition on u(r)u(r) at r=0r=0, treating l=0l=0 separately from l≥1l\ge 1.

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