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K: Fachverband Kurzzeitphysik

K 5: Laserstrahlwechselwirkung und Laseranwendungen

K 5.3: Vortrag

Dienstag, 26. Februar 2013, 14:30–14:45, HS 4

Ultrafast electron kinetics in SiO2 under X-ray femtosecond irradiation — •Nikita Medvedev and Beata Ziaja — Center for Free Eelectron Laser Science (CFEL at DESY), Notkestr. 85, 22706 Hamburg

When a dielectric is irradiated with an ultrashort laser pulse at X-ray photon energy, various physical processes take place. The photons are absorbed mostly by the deep-shell electrons, which are then excited to the high energy states of the conduction band and/or to the continuum. These electron propagate further and perform secondary scatterings via elastic and inelastic channels. All these processes occur on femtosecond timescales. Material properties are then defined by the transient state of the electronic distribution within the solid. In this contribution we present a theoretical study of the ultrafast electron kinetics in solid SiO2, irradiated with the femtosecond X-ray laser pulse (~40 fs duration). The Monte-Carlo code, similar to [1,2], is applied to model the electron kinetics, which includes the primary ionization, secondary scattering of electrons, and Auger-decays of deep-shell holes. With the calculated transient electron density, the transient change of the optical properties (reflection, transmittance of visible light) of the material is estimated. The analysis of the results allows us to conclude that in the X-ray excited dielectric, the holes in the valence band give the dominant contribution to the the optical properties of the material on femtosecond scales.

[1] N. Medvedev, B. Rethfeld, NJP 12, 073037 (2010) [2] B. Ziaja, R.A. London, J. Hajdu, JAP 97, 064905 (2005)