Using the photo-induced $L_3$ resonance shift in Fe and Ni as time reference for ultrafast experiments at low flux soft X-ray sources

Abstract

We study the optical-pump induced ultrafast transient change of the X-ray absorption at the $L_3$ absorption resonances of the transition metals Ni and Fe in Fe${}_{0.5}$Ni${}_{0.5}$ alloy. We find the effect for both elements to occur simultaneously on a femtosecond timescale. This effect may hence be used as a handy cross-correlation scheme providing a time-zero reference for ultrafast optical-pump soft X-ray-probe measurement. The method benefits from a relatively simple experimental setup as the sample itself acts as time-reference tool. In particular, this technique works with low flux ultrafast soft X-ray sources. The measurements are compared to the cross-correlation method introduced in an earlier publication.

12 pages, 3 figures

References in corpus (2)

• Femtosecond x-ray absorption spectroscopy of spin and orbital angular momentum in photoexcited Ni films during ultrafast demagnetization
• Influence of laser-excited electron distributions on the x-ray magnetic circular dichroism spectra: Implications for femtosecond demagnetization in Ni