Quantum Mechanics: Concepts and Applications · Problem 5.28

Three-Dimensional Problems — Nouredine Zettili

Physics — Quantum Mechanics · angular-momentum-eigenstate-superposition

Problem

Consider a system which is given in the following angular momentum eigenstates ∣l, m⟩|l,\ m\rangle: ∣ψ⟩=17∣1, −1⟩+A∣1, 0⟩+27∣1, 1⟩,|\psi\rangle = \frac{1}{\sqrt{7}}|1,\ -1\rangle + A|1,\ 0\rangle + \sqrt{\frac{2}{7}}|1,\ 1\rangle, where AA is a real constant. (a) Calculate AA so that ∣ψ⟩|\psi\rangle is normalized. (b) Calculate the expectation values of L^x\hat{L}_x, L^y\hat{L}_y, L^z\hat{L}_z, and L^2\hat{L}^2 in the state ∣ψ⟩|\psi\rangle. (c) Find the probability associated with a measurement that gives 1ℏ1\hbar for the zz-component of the angular momentum. (d) Calculate ⟨1, m∣L^+2∣ψ⟩\langle 1,\ m|\hat{L}_+^2|\psi\rangle and ⟨1, m∣L^−2∣ψ⟩\langle 1,\ m|\hat{L}_-^2|\psi\rangle.

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