David Prendergast (Extra SIMES Seminar)

Date/Time
Date(s) - Dec 8 2014
11:15 AM - 12:15 PM

Location
Shasta Room, Bldg. 40, Room 361

Category(ies)


Interpretation of ultrafast time-resolved core-level spectroscopies using static and time-dependent density functional theory approaches

 David Prendergast

The Molecular Foundry, Berkeley Lab

 

The availability of ultrafast x-ray pulses, both from powerful free-electron laser light-sources as well as table-top high-harmonic-generation, has significantly enhanced the utility of core-level spectroscopies as probes for investigating dynamical processes in functional materials on femtosecond timescales. Theoretical approaches to complement these time-domain experiments are therefore actively being developed. While real-time dynamical simulations of core-level spectroscopies are still in their infancy, first-principles approaches regularly deployed in the interpretation of static core-level spectroscopies can be usefully adapted to help interpret spectral signatures obtained from time-resolved measurements. Two illustrative case studies will be presented: (1) Using a combination of constrained density functional theory (c-DFT) and time-dependent density functional theory (TD-DFT) we interpret measured transient core-level shifts in femtosecond time-resolved x-ray photoelectron spectroscopy, investigating the photo-induced dynamics of electron injection from a Ru-N3 dye molecule chemisorbed onto a ZnO substrate [1]; (2) Using non-equilibrium electron-hole densities obtained from real-time TD-DFT simulations of the valence electronic structure [2,3] we estimate the transient modulation of the L-edge x-ray absorption in femtosecond laser-excited silicon, as observed using attosecond XUV pulses. An analysis of these simulations, while taking into account the approximations involved, can provide valuable insights into the nature of the underlying electron dynamics.

 

References:

[1] Siefermann et al., J. Phys. Chem. Lett. 5, 2753 (2014).

[2] Yabana et al., Phys. Rev. B 85, 045134 (2012).

[3] Dutoi et al., Phys. Rev. A 88, 013419 (2013).