  Modeling nuclear reaction networks for nuclear science applications and for
simulations of astrophysical environments relies on cross section data for a
vast number of reactions, many of which have never been measured.
  In this paper we examine the validity of the Weisskopf-Ewing approximation
for determining unknown (n,n') and (n, 2n) cross sections from surrogate data.
Using statistical reaction calculations with realistic parameterizations, we
investigate first whether the assumptions underlying the Weisskopf-Ewing
approximation are valid for (n,n') and (n, 2n) reactions on representative
target nuclei. We then produce simulated surrogate reaction data and assess the
impact of applying the Weisskopf-Ewing approximation when extracting (n,n') and
(n, 2n) cross sections in situations where the approximation is not strictly
justified.
  We find that peak cross sections can be estimated using the Weisskopf-Ewing
approximation, but the shape of the (n,n') and (n,2n) cross sections,
especially for low neutron energies, cannot be reliably determined without
accounting for the angular-momentum differences between the neutron-induced and
the surrogate reaction.
