such energy eigenstates. If Y d x ≤ ≤ δ δ E , all these energy eigenstates will move into the range between E and E + δ δ E and contribute to an increase in Ω Ω . The number of energy eigenstates that move from below E + δ δ E to above E + δ δ E is, of course, given by N Y ( E + δ δ E ) . The difference