3

Quantum Harmonic Oscillator

medium30 pts

Statement#

A quantum harmonic oscillator has potential energy: V(x)=12mω2x2V(x) = \frac{1}{2}m\omega^2 x^2

Find:

  1. The ground state energy E0E_0
  2. The normalized ground state wave function ψ0(x)\psi_0(x)

Required Topics#

  • Time-independent Schrödinger equation
  • Gaussian wave functions
  • Normalization integrals
  • Quantum harmonic oscillator
  • Zero-point energy

The Schrödinger Equation#

22md2ψdx2+12mω2x2ψ=Eψ-\frac{\hbar^2}{2m}\frac{d^2\psi}{dx^2} + \frac{1}{2}m\omega^2x^2\psi = E\psi

Strategy#

  1. Try a Gaussian form: ψ0(x)=Aeαx2\psi_0(x) = Ae^{-\alpha x^2}
  2. Compute the first and second derivatives
  3. Substitute into the Schrödinger equation
  4. Match coefficients to find α\alpha and E0E_0
  5. Normalize to find AA

Useful Integral#

eax2dx=πa\int_{-\infty}^{\infty} e^{-ax^2} dx = \sqrt{\frac{\pi}{a}}

x2eax2dx=12πa3\int_{-\infty}^{\infty} x^2 e^{-ax^2} dx = \frac{1}{2}\sqrt{\frac{\pi}{a^3}}

What to Find#

  1. Ground state energy: E0E_0 in terms of \hbar and ω\omega
  2. Wave function: ψ0(x)\psi_0(x) (properly normalized)
  3. Show that α=mω2\alpha = \frac{m\omega}{2\hbar}

Solution#

Solution coming soon.

Hints (4)

Topics Needed

harmonic-oscillatorladder-operatorsground-state

Prerequisites

  • schrodinger-equation
  • gaussian-integrals
  • hermite-polynomials

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