Breathing mode dynamics and elastic properties of gold nanoparticles.

We present calculations of the bulk modulus, heat capacity, and the period of the breathing mode for spherical nanoparticles following excitation by ultrafast laser pulses. The bulk modulus and heat capacities both exhibit clear transitions upon bulk melting of the particles. Equilibrium calculations of the heat capacity show that the melting transition is sharper and occurs at a lower temperature than one would observe from an ultrafast experiment.

Combination of perturbative and variational methods for calculating molecular spectra: calculation of the upsilon=3-5 CH stretch overtone spectrum of CHF3.

Highly excited states of the CHF3 molecule belonging to the third, fourth, and fifth Fermi polyad are calculated using a combination of the Van Vleck perturbation theory and a variational treatment. The perturbation theory preconditions the Hamiltonian matrix by transforming away all couplings except those between nearly degenerate states. This transformation is implemented so that eigenvalues can be found with significantly smaller matrices than that which would be needed in the original normal mode representation.