Consider a transition from ni→nf,
EΔh1=mc21aψi(aψf−aψi)
Consider another transition from aψf+aψi→aψf, (This is an extrapolation, it is not proven that aψf+aψi is a solution.)
EΔh2=mc2aψf+aψi(aψf−(aψf+aψi))=mc2aψf+aψi(−aψi)
such that, aψi is in between the paths of EΔh1 and EΔh2.
If we take the geometric mean of the two,
ˉEΔh=√EΔh1.EΔh2=mc2√aψi−aψfaψf+aψi
and let
Eo=−ˉEΔhaψi=−mc21aψi√aψi−aψfaψf+aψi Jm-1
We have an expression for Eo. A negative sign is necessary because a change from a higher value of aψ to a lower value of aψ (ie. a positive value of (aψi−aψf) ) results in a loss of energy.
Note: If,
EΔhf=2πaψfmc.f
EΔhi=2πaψimc.f
And,
EΔhi+EΔhf=2πaψimc.f+2πaψfmc.f
2π(aψi+aψf)mc.f=EΔhi+f
And,
EΔhi+f=mc2aψf+aψi(aψf−(aψf+aψi)) --- (*)
This does not proof that aψf+aψi is a solution to x for ψ but it shows that (*) is a valid expression.