  Whenever real particle production occurs in quantum field theory, the
imaginary part of the Hadamard Elementary function $G^{(1)}$ is non-vanishing.
A method is presented whereby the imaginary part of $G^{(1)}$ may be calculated
for a charged scalar field in a static spherically symmetric spacetime with
arbitrary curvature coupling and a classical electromagnetic field $A^{\mu}$.
The calculations are performed in Euclidean space where the Hadamard Elementary
function and the Euclidean Green function are related by $(1/2)G^{(1)}=G_{E}$.
This method uses a $4^{th}$ order WKB approximation for the Euclideanized mode
functions for the quantum field. The mode sums and integrals that appear in the
vacuum expectation values may be evaluated analytically by taking the large
mass limit of the quantum field. This results in an asymptotic expansion for
$G^{(1)}$ in inverse powers of the mass $m$ of the quantum field.
Renormalization is achieved by subtracting off the terms in the expansion
proportional to nonnegative powers of $m$, leaving a finite remainder known as
the ``DeWitt-Schwinger approximation.'' The DeWitt-Schwinger approximation for
$G^{(1)}$ presented here has terms proportional to both $m^{-1}$ and $m^{-2}$.
The term proportional to $m^{-2}$ will be shown to be identical to the
expression obtained from the $m^{-2}$ term in the generalized DeWitt-Schwinger
point-splitting expansion for $G^{(1)}$. The new information obtained with the
present method is the DeWitt-Schwinger approximation for the imaginary part of
$G^{(1)}$, which is proportional to $m^{-1}$ in the DeWitt-Schwinger
approximation for $G^{(1)}$ derived in this paper.
