# Trapped Electrons

1. Nov 22, 2008

### emperrotta

the textbook states, by the equation:

hf = $$\Delta$$E = Ehigh - Elow

If an electron confined to a one-dimensional infinite potential well is to absorb a photon, the energy hf of the photon must equal the energy difference $$\Delta$$E between the initial energy level of the electron and a higher level.

Then as an aside, the textbook states:
Although the above equation and what we have discussed about photon absorption and emission can be applied to physical (real) electron traps, they actually cannot be applied to one-dimensional (unreal) electron traps. The reason involves the need to conserve angular momentum in a photon absorption or emission process.

I do not understand this statement about angular momentum.

2. Nov 22, 2008

### borgwal

It's because a photon carries angular momentum, but in 1-D the concept of angular momentum is not defined.