Coherent excitation of vibrational modes in nanoparticles and nanorods: What do we really measure?

Abstract

In this paper the dynamical response of cylindrical nanorods to ultrafast laser-induced heating is examined. Theoretical analysis predicts that a thermal pulse should excite both extensional and breathing vibrational modes of the rods. Analytical formulae for the frequencies of these modes are derived assuming that the length of the rods is much greater than their radii. Because the frequency of the fundamental extensional mode is much lower than that of the breathing mode, the extensional mode is expected to dominate the response for a real experiment, i.e., for a finite-time heating/expansion process. The results of this model are compared to data from transient absorption experiments perf..