We investigate the vibration dynamics of ellipsoidal silver nanoparticles, using time-resolved optical pump-probe spectroscopy. When excited with femtosecond laser pulses, the particles execute anisotropic shape oscillations. We show that these vibrations are triggered by the thermal expansion of the optically heated particles. The time dependence of the vibrations indicates that this expansion is caused by two mechanisms: The lattice anharmonicity and the extremely large pressure of the hot conduction electrons.

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The fluorescence and fluorescence-excitation spectra of Cm in a hydrocarbon glass at 1.2 K are reported. The fluorescence spectrum resembles that of a molecular X-trap in crystalline Cm. The vibronic bands in these spectra are assigned, and the intensity distribution among the false origins points to vibronic coupling within the singlet manifold. The lowest excited singlet state of Cm shows predominantly TI, and G, character.Additionally, we show that a reduction of the symmetry of Cw by either an intra-or an intermolecular perturbation leads to a fluorescence spectrum with a strong 0-0 transition and a different vibronic structure.

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