Regensburg 2007 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 20: Poster session

MM 20.53: Poster

Dienstag, 27. März 2007, 14:45–18:00, Poster C

Photoinduced ultrafast volume changes in intermediate valence solids — •momar diakhate and martin garcia — Theoretishe, physik,Universitat Kassel,D-34132 Kassel, Germany

We present a theoretical model for the description of the ultrafast structural response of intermediate valence solids to femtosecond laser excitation. Based on the promotional Ramirez-Falicov model we consider the femtosecond laser heating of gamma-Cerium and the subsequent ultrafast lattice expansion dynamics.

In particular we determine the thermodynamic and electronic properties of cerium at very high electronic temperatures (simulating the laser excitation). The possibility for a non-equilibrium photoinduced inverse volume collapse transition is discussed. The p-v-T equation of state is obtained from the Helmoltz free energy in the usual way of thermodynamic derivatives by considering an adiabatic expansion of the crystal at high temperature. We take into account both the laser excited and the unexcited parts of the system, in oder to account for inertial confinement.

By means of the Hugoniot theory the shock velocity variation in the surrounding (unheated) part of the sample was obtained and used to calculate the time dependence of the thermodynamic properties in the heated material.