Consider a function so constructed such that,
Zs=dβef(Es)dEs=βf′(Es)ef(Es)
where β is a constant, and f(Es) is a function in Es with roots Esi i=1,2,3.... ie.
f(Es=Esi)=0i=1,2,3...
then
ef(Es=Esi)=e0=1
and,
[dβef(Es)dEs]Esi=βf′(Es=Esi).1=Zsi
Since differentiation by product rule leaves behind one term without each root factor, we define,
f′(Esi)=p(Zsi).(Esi−Es1)(Esi−Es2)..
except for the factor of (Esi−Esi) such that,
f′(Esi)=p(Zsi).n∏j=1j≠i(Esi−Esj)=Zsiβ
where p(Zsi) is defined by,
p(Zsi)=Zsiβ.n∏j=1j≠i(Esi−Esj)
where we insist that Esi≠Esj for i≠j, each root of f(Es) is unique. p(Zsi) can also be defined as p(Esi) as
p′(Es)∏i(Es−Esi) is zero for all Es=Esi. We will still have,
p(Esi)=Zsiβ.n∏j=1j≠i(Esi−Esj)
β is defined such that,
∫Esmax0ZsdEs=Z=[βef(Es)]Esmax0=alli∑iZsi
β=Z[ef(Es)]Esmax0
If ef(Esmax)→0 for Esmax→∞
β=Z0−ef(0)=−Zef(0)
at ef(Es=0).
Notice the expression for Z is always zero integrating from root to root of f(Es). This is because ef(Es) intersect y=1 repeatedly such that the area above and below the x-axis of ef(Es) is equal, from root to root of f(Es). This means, the value of Z is determined by that part of the curve from zero to the first root of f(Es) and, the last root of f(Es) to the tail end of ef(Es) towards infinity.
If the first root is zero then β can be found from,
β=Z0−ef(Eslast)=−Zef(Eslast)=−Z
because we know that the integration of Zs with boundaries between roots of f(Es) sums to zero.
No need to involve T, which ever way temperature is defined.