Measuring transient states of matter using incoherent scattering
Measuring transient states of matter on the femto- to attosecond timescale is a current scientific challenge. Particularly for nanometer sized objects, the size of biomolecules for example proteins, it is a challenge to measure signal above the noise level due to low cross-sections. The amount of photons LCLS produces can overcome signal-to-noise issues and opens the door to perform measurements in entirely new regimes. In the featured and recently published study, we make use of LCLS in such a new way and measure an incoherent signal much above the noise level. The basis of this experiments is to spectrally resolve the scattering from free electrons or Thomson scattering. The developed method allows another way to gain insight into transient states, for example, the nanoplasma transformation or chemical reactions that last on the atto- to picosecond timescale. Particularly, parameters such as (electron) temperature, density and ionization levels can be measured using the LAMP endstation at LCLS. To make the proof-of-principle study, a pump-probe scheme was employed that first used an IR laser to induce a transient state (nanoplasma) in a nano-sample (argon clusters) and then secondly, after a time-delay, measures this state using the X-rays LCLS.