Attosecond - picometer resolution science is .. a hand away.

 

12 Octave Coherent High Harmonics’ X-ray Supercontinua Enable Ultra-Precise Measurements on a Tabletop.


      

Coherent X-rays are an ideal probe of the ultra-fast and ultra-small atomic and molecular world, due to their nature of having extremely short wavelength, short pulse duration, unique ability to penetrate thick and opaque objects combined with elemental specific fingerprints from the atomic absorption edges.
The large synchrotron and free electron laser facilities are the forefront of science, however tabletop sources are becoming more and more capable of performing complimentary invivo studies in the biological and material sciences. The other alternative source, the high harmonics, originate from a highly nonlinear process of energy upshift, when a high power laser is focused into a gas with intensities close to the binding atomic potentials. In this process thousands of photons can add to create a single photon with X-ray energy.




      

While Ultrafast spectroscopies in the visible and infrared (IR) energy regions can probe non-equilibrium dynamics on the ultrafast time scale, they cannot determine the chemical nature of the excited state dynamics with elemental selectivity. Alternatively, coherent X-ray spectroscopies have an important additional advantage of being able to uncover oxidation state, magnetic state, or charge localization to specific elements, giving information about the electronic structures, (i.e., valence, bands and charge), as well as orbital and spin ordering phenomena.




Today, atomic structure can be determined routinely using incoherent X-ray crystallography techniques. Unlike X-ray crystallography, which requires samples to be crystalline, XAFS spectroscopy can extract dynamic local structure information from various phases (i.e crystals, gases, low concentration solutions, disordered solids etc.), with some prior knowledge. Making it a viable computational imaging technique at the attosecond - picometer scale on up.
The near- and extended- X-ray absorption fine structure (XAFS) is a universal response of matter interacting with X-ray light near an absorption edge. This quantum phenomenon can be understood in a simple three-step model, where an incident X-ray is absorbed by an atom, which leads to the ejection of a photoelectron from a core-shell. Then the photoelectron is scattered from neighboring non-excited atoms, and the quantum interferences of the outgoing and incoming scattered electron waves lead to an energy-dependent variation of the X-ray absorption probability. With some prior knowledge, these techniques can provide full spatio-temporal and chemical imaging information (4+1D) of the local atomic structure of materials, including 1) the types of atoms that are present, coordination numbers (number of neighboring atoms at particular distances), inter-atomic distances, as well as disorder (using EXAFS), and 2) the oxidation state, and coordination chemistry (i.e., symmetries, isomerism, etc.) (using NEXAFS).
Using coherent high harmonic supercontinua laser-like beams, high quality extended edge coherent absorption spectroscopy of materials have been observed in the near-keV region for the first time, to obtain structural and chemical information. Published in Phys. Rev. Lett. 2018, DOI: 10.1103/PhysRevLett.120.093002
In the near future, because high harmonic X-ray bursts emerge as an isolated femtosecond-to-attosecond pulses, it will be possible to perform extensive spatio-temporal and chemical imaging of the local atomic structure of materials.
 The attosecond -picometer resolution science is .. a hand away.


cite as:
[1]. Popmintchev, Dimitar, et. al., Phys. Rev. Lett. 120, 093002, 1 March 2018 DOI: Phys. Rev. Lett. 2018, DOI: 10.1103/PhysRevLett.120.093002
[2]. Popmintchev, Dimitar, "Quantum and Extreme Nonlinear Optics Design of Coherent Ultrafast X-ray Light and Applications" ISBN 9781369490015 2016 https://www.amazon.com/dp/B01N9G9JVZ
[3]. Popmintchev, Tenio, et. al., Science  Vol. 336, Issue 6086, pp. 1287-1291 08 Jun 2012  DOI: Science, DOI: 10.1126/science.1218497 

No comments:

Post a Comment