A Modern Approach to Quantum Mechanics · Problem 10.2

Time-Independent Perturbations — John S. Townsend

Physics — Quantum Mechanics · hydrogen-atom-expectation-values

Problem

An electron in the Coulomb field of the proton is in the state ∣ψ⟩=45∣1,0,0⟩+3i5∣2,1,1⟩|\psi\rangle = \frac{4}{5}|1, 0, 0\rangle + \frac{3i}{5}|2, 1, 1\rangle where ∣n,l,m⟩|n, l, m\rangle are the usual energy eigenstates of hydrogen. (a) What is ⟨E⟩\langle E \rangle for this state? What are ⟨L2⟩\langle \mathbf{L}^2 \rangle and ⟨Lz⟩\langle L_z \rangle? (b) What is ∣ψ(t)⟩|\psi(t)\rangle? Which of the expectation values in (a) vary with time?

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