PX284 - E5b - harmonic oscillator in 3D

E = (n_{x} + \frac{1}{2}) ℏ ω + (n_{y} + \frac{1}{2}) ℏ ω + (n_{z} + \frac{1}{2}) ℏ ω

Z_{3 D} = Z_{x} Z_{y} Z_{z} = (Z_{1 D})^{3}

U_{3 D} = 3 U_{1 D}