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# Bound-State Solutions of the Schrödinger Equation by Numerical Integration

This Demonstration shows the mathematical solution of the time-independent Schrödinger equation for two potentials, the harmonic oscillator and an anharmonic oscillator with . The wavefunction is fixed at . You can obtain linearly independent solutions by numerical integration for different values of the derivative and the energy level . The vertical dashed lines indicate the locations of the classical turning points.
For any value of , it is always possible to tune in a value of such that goes to zero either in the limit as or in the limit as . The goal is to find the discrete values of (the eigenvalues) such that an acceptable solution (the eigenfunction) exists that goes to zero for both limits and .
The eigenvalues of the harmonic oscillator are , , , , …. The first five eigenvalues of the anharmonic oscillator are , , , , and .
Units are such that , , and the proportionality coefficients in the potential functions are as indicated.

### DETAILS

This Demonstration is inspired by section 5.7 of [1].
Snapshot 1: Harmonic oscillator with . The particular solution with behaves well in the limit as but not in the limit as . Therefore, is not an eigenvalue.
Snapshot 2: Harmonic oscillator with . The particular solution with behaves well in the limit as but not in the limit as . Therefore, is not an eigenvalue.
Snapshot 3: Harmonic oscillator with . The particular solution with behaves well in both limits as and . Therefore, is an eigenvalue (first excited state).
Snapshot 4: Anharmonic oscillator with . The particular solution with behaves well in both limits as and . Therefore, is an eigenvalue (ground state).
Snapshot 5: Anharmonic oscillator with . The particular solution with behaves well in both limits as and . Therefore, is an eigenvalue (fourth excited state).
Reference
[1] R. Eisberg and R. Resnick, Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles, New York: Wiley, 1985.

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