Academics

Femtosecond response of polyatomic molecules to ultra-intense hard X-rays

(DESY/Science Communication Lab)

The study of molecules with X-rays is of particular interest for biological and potentially pharmaceutical sciences. X-rays are here being used to resolve the shape or structure of a molecule. But when the X-rays interact with the molecules, the ionize the atoms the molecule consists of and the molecule is transformed into a nanoplasma. Such radiation damage is of particular interest, as a solid understanding of the underlying damaging processes is required to lead to high-res imaging. In the linked study that has been published in Nature, we investigate molecules using intense hard X-rays from the CXI instrument at LCLS reaching a never before seen level of ionization. The insights of this study help developing high-resolution imaging of bio molecules.

Read more

Image from: DESY/Science Communication Lab

Measuring transient states of matter using incoherent scattering

Thomson Scattering MacDonald

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.

Read more

Ultrafast x-ray-induced nuclear dynamics in diatomic molecules

PRA Picon 2016 07This is a similar study to our work published in Nature Communications earlier this year. Here, we investigate diatomic molecules and use a two-color X-ray pump–X-ray probe approach. The pump pulse arrives first and induces dynamics, whereas the probe pulse arrives at a certain time delay and allows us to look at the induced dynamics. Theoretic predictions align well with the observed dynamics, such that we establish a microscopic understanding of the processes. The work has been mainly driven by A. Picon and C.S. Lehmann, whom I particularly congratulate to this paper. Please find more at.

Read more

Coherent diffraction of Rice Dwarf virus at the Linac Coherent Light Source

nature data cover

In this study, we've applied coherent diffractive imaging to study the structure of a single Rice dwarf virus. The CXI instrument at the Linac coherent light source focuses 1012 photons into a nanometer-sized area. Here the X-rays scatter of a single virus particle and create a snapshot of the virus. The acquired dataset of this study has been published in Nature scientific data, that allows access to the actual dataset. The publication yields information on how to access the data and background information as well. This result comes out of a large collaboration, the Single particle initiative, where scientists from around the world have united to pull on one string and push the method of Single particle imaging to the next level.

Read more

Stimulated x-ray Raman Scattering

Faraday discussion stimulated emissionOur critical assessment with stimulated Raman scattering using X-Ray free electron lasers (FEL) was recently published in the journal Faraday Discussions. Stimulated Raman scattering or inelastic scattering promises new opportunities to follow electron transfers in chemical reactions. Ultrafast, time-resolved measurements are a cornerstone of FEL science and this method would enable us to broaden the accessible wavelength regime. Our assessment shows current opportunities and limitations of this technique that will become particularly interesting with new superconducting linac light sources, for example, XFEL and Hamburg and LCLS-II. It is foreseen that these new light sources will have much-improved beam characteristics that are particularly interesting for stimulated Raman scattering.

Read more

Directions

max bucherOn this page, I link some of my recent work and advances from my collaborations that got promoted by other institutes. Use the tags below this box to find more of my related work by keyword.

Social Media

Please find me also on social media pages.

 

Contact Me

+49(0)611 536-200
 

Kurhausplatz 1
D-65189 Wiesbaden
 

This email address is being protected from spambots. You need JavaScript enabled to view it.