However, if there is an energy difference between the two states, then nontrivial dynamics can occur.

The kinetic energy difference would be enough to blast a city.

The energy difference between the 6d and 5f subshells is very low.

Just as plants love the sun, there are creatures that can use the energy differences down at that edge.

The energy difference between these 2 sets of d-orbitals is now called Δ.

Note that the first term is the expected value of the energy difference, while the second is essentially its variance.

The energy difference also introduces a non-randomness at the local molecular level.

Let the energy difference between the states be so that is the transition frequency of the system.

The energy difference between the two states is so small their populations vary significantly with temperature.

This changes the energy difference between the ground and first excited states.