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[求助] Kramers-Kronig Relations 推导介电常数已有2人参与

希望用epsilon2推导epsilon1，已经找到了别人的matlab程序，但是看不懂input中的alpha（the value of the moment considered）指的是什么意思，另外两个参数omiga，imchi都有。不知道alpha该怎么设置。
%The program inputs are 1) omega, vector of the frequency
%(or energy) components, 2) imchi, vector of the imaginary
%part of the susceptibility under examination, and 3) alpha,
%the value of the moment considered. The two vectors
%1) and 2) must have the same length.
%The output is the estimate of the real part as obtained
%with K-K relations.
%In order to use this program, save the whole text contained
%in this section in a file and name it kkrebook.m
if size(omega,1)>size(omega,2);
omega=omega';
end;
if size(imchi,1)>size(imchi,2);
imchi=imchi';
end;
%Here the program rearranges the two vectors so that,
%whichever their initial shape, they become row vectors.
g=size(omega,2);
%Size of the vectors.%
rechi=zeros(size(imchi));
%The output is initialized.
a=zeros(size(imchi));
b=zeros(size(imchi));
%Two vectors for intermediate calculations are initialized
deltaomega=omega(2)-omega(1);
%Here we compute the frequency (or energy) interval
j=1;
beta1=0;
for k=2:g;
b(1)=beta1+imchi(k)*omega(k)^(2*alpha+1)/...
(omega(k)^2-omega(1)^2);
beta1=b(1);
end;
rechi(1)=2/pi*deltaomega*b(1)*omega(1)^(-2*alpha);
%First element of the output: the principal part integration
%is computed by excluding the first element of the input
j=g;
alpha1=0;
for k=1:g-1;
a(g)=alpha1+imchi(k)*omega(k)^(2*alpha+1)/...
(omega(k)^2-omega(g)^2);
alpha1=a(g);
end;
rechi(g)=2/pi*deltaomega*a(g)*omega(g)^(-2*alpha);
%Last element of the output: the principal part integration
%is computed by excluding the last element of the input
for j=2:g-1; ;
%Loop on the inner components of the output vector.
alpha1=0;
beta1=0;
for k=1:j-1;
a(j)=alpha1+imchi(k)*omega(k)^(2*alpha+1)/...
(omega(k)^2-omega(j)^2);
alpha1=a(j);
end;
for k=j+1:g;
b(j)=beta1+imchi(k)*omega(k)^(2*alpha+1)/...
(omega(k)^2-omega(j)^2);
beta1=b(j);
end;
rechi(j)=2/pi*deltaomega*(a(j)+b(j))*omega(j)^(-2*alpha);
end;
%Last element of the output: the principal part integration
%is computed by excluding the last element of the input

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