  Transient absorption and Raman scattering measurements on noble metal
nanoparticles offer complimentary information on their vibrational modes and
mechanical interactions with their surroundings. We have developed a
comprehensive modeling tool for simulating both of these spectra based on
COMSOL Multiphysics finite-element simulation software. This application can be
used to predict the spectra for arbitrary geometries and metal compositions,
takes into account local changes in dielectric function for the metals, and can
model the small vibrational amplitudes of real transient absorption
measurements. We present simulation results for gold and silver nanospheres,
silver nanocubes, and gold truncated nanocubes, showing the ability to
calculate relative peaks heights in Raman spectra and the ability to fit
amplitudes of transient-absorption signals to experiment, and showing that
Raman spectra can include contributions from modes often neglected due to
symmetry considerations.
