  In ultrafast electron diffraction (UED) experiments, accurate retrieval of
time-resolved structural parameters, such as atomic coordinates and thermal
displacement parameters, requires an accurate scattering model. Unfortunately,
kinematical models are often inaccurate even for relativistic electron probes,
especially for dense, oriented single crystals where strong channeling and
multiple scattering effects are present. This article introduces and
demonstrates dynamical scattering models tailored for quantitative analysis of
UED experiments performed on single-crystal films. As a case study, we examine
ultrafast laser heating of single-crystal gold films. Comparison of kinematical
and dynamical models reveals the strong effects of dynamical scattering within
nm-scale films and their dependence on sample topography and probe kinetic
energy. Applying to UED experiments on an 11 nm thick film using 750 keV
electron probe pulses, the dynamical models provide a tenfold improvement over
a comparable kinematical model in matching the measured UED patterns. Also, the
retrieved lattice temperature rise is in very good agreement with predictions
based on previously measured optical constants of gold, whereas fitting the
Debye-Waller factor retrieves values that are more than three times lower.
Altogether, these results show the importance of dynamical scattering theory
for quantitative analysis of UED and demonstrate models that can be practically
applied to single-crystal materials and heterostructures.
