w=zetaf(z) is the plasma dispersion function , which also is based on
The Faddeeva or Kramp function . The Faddeeva or Kramp function
is defined as:
Faddeeva(z)=exp(-z^2)erfcx(z)
where erfcx(z)=erfc(-iz) which is the complex complementary error
function. And the general plasma dispersion function has the relationship
of Faddeeva function:
w=zetaf(z)=i \sqrt(pi) Faddeeva(z).
This algorithm is based on the work:
Mofreh R. Zaghloul and Ahmed N. Ali, "Algorithm 916: Computing the Faddeyeva and Voigt Functions," ACM Trans. Math. Soft. 38 (2), 15 (2011).