The effects of metal core dimension,oxide shell thickness and ellipsoid aspect ratio of Al-Al-Al2O3core-shell nanoparticles on the near-infrared and visible absorption spectra of nanocomposite Al-Al-Al2O3/nitrocellulose(NC) film are investigated by numerical calculations.Both the size-dependent interband transitions and frequency-dependent free electron damping of the nanometallic aluminium are taken into account in the calculations.Oxidation effect of nanoaluminium is also analysed.It is shown that oxidation may enhance but may also reduce the optical absorption,depending on the excited light energy and initial dimension of nanoparticle.Metal core size and excited light energy dominate the absorption characteristic.The absorption ability of ellipsoidal nanoparticles is larger than that of spheroidal nanoparticles and increases by the square index as the aspect ratio increases.These calculations will provide some significant theoretical guidance for the preparation and laser ignition of nanoenergetic materials.
This paper demonstrates the femtosecond time-resolved coherent anti-Stokes Raman scattering by using folded BOXCARS geometry where an ultrashort broadband coherent white light continuum was used as Stokes pulse, and carries out the non-contact detection at long distance. The CARS signal is so easy to be detected that it can be seen even by nude eye. The C-H bonds of chloroform or PMMA were detected and the vibration modes belonging to the side chain and the main chain in PMMA were also compared. Their vibrational characteristics involved decay process and quantum beating were discussed. This modified CARS experimental technique could make up the deficiency of traditional CARS technique.
A modified model, a set of rate equations based on time-dependent correlation function, is used to study vibrational relaxation dynamics in transient grating spectroscopy. The dephasing, the population dynamics, and the vibrational coherence concerning two vibrational states are observed respectively in organic dye IR780 perchlorate molecules doped polyvinyl alcohol matrix. The result shows that in addition to the information concerning system-environment interac- tion and vibrational coherence, the vibrational energy transfer can be described by this modified model.
