# This Quantum World/Implications and applications/Time independent Schrödinger equation

## Time-independent Schrödinger equation

If the potential V does not depend on time, then the Schrödinger equation has solutions that are products of a time-independent function ${\displaystyle \psi (\mathbf {r} )}$  and a time-dependent phase factor ${\displaystyle e^{-(i/\hbar )\,E\,t}}$ :

${\displaystyle \psi (t,\mathbf {r} )=\psi (\mathbf {r} )\,e^{-(i/\hbar )\,E\,t}.}$

Because the probability density ${\displaystyle |\psi (t,\mathbf {r} )|^{2}}$  is independent of time, these solutions are called stationary.

Plug ${\displaystyle \psi (\mathbf {r} )\,e^{-(i/\hbar )\,E\,t}}$  into

${\displaystyle i\hbar {\frac {\partial \psi }{\partial t}}=-{\frac {\hbar ^{2}}{2m}}{\frac {\partial }{\partial \mathbf {r} }}\cdot {\frac {\partial }{\partial \mathbf {r} }}\psi +V\psi }$

to find that ${\displaystyle \psi (\mathbf {r} )}$  satisfies the time-independent Schrödinger equation

${\displaystyle E\psi (\mathbf {r} )=-{\hbar ^{2} \over 2m}\left({\frac {\partial ^{2}}{\partial x^{2}}}+{\frac {\partial ^{2}}{\partial y^{2}}}+{\frac {\partial ^{2}}{\partial z^{2}}}\right)\psi (\mathbf {r} )+V(\mathbf {r} )\,\psi (\mathbf {r} ).}$