Probing warm dense matter using femtosecond X-ray absorption spectroscopy with a laser-produced betatron source

• Published in: Nature communications Vol. 9; no. 1; pp. 3276 - 6
• Main Authors: Mahieu, B., Jourdain, N., Ta Phuoc, K., Dorchies, F., Goddet, J.-P., Lifschitz, A., Renaudin, P., Lecherbourg, L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16-08-2018; Nature Publishing Group; Nature Portfolio
• Subjects: 140/125; 639/624/1020/1095; 639/766/1960/1135; 639/766/1960/1137; 639/766/400/1106; Absorption spectroscopy; Electron energy; Femtosecond pulses; Humanities and Social Sciences; Laser radiation; Lasers; multidisciplinary; Optics; Physics; Plasma interactions; Science; Science (multidisciplinary); Spectrum analysis; X ray sources; X-ray absorption spectroscopy; X-ray spectroscopy; FREE-ELECTRON LASER; SPIN-CROSSOVER DYNAMICS; GOLD
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-05791-4

Exploring and understanding ultrafast processes at the atomic level is a scientific challenge. Femtosecond X-ray absorption spectroscopy (XAS) arises as an essential experimental probing method, as it can simultaneously reveal both electronic and atomic structures, and thus potentially unravel their nonequilibrium dynamic interplay which is at the origin of most of the ultrafast mechanisms. However, despite considerable efforts, there is still no femtosecond X-ray source suitable for routine experiments. Here we show that betatron radiation from relativistic laser−plasma interaction combines ideal features for femtosecond XAS. It has been used to investigate the nonequilibrium dynamics of a copper sample brought at extreme conditions of temperature and pressure by a femtosecond laser pulse. We measured a rise-time of the electron temperature below 100 fs. This experiment demonstrates the great potential of the table-top betatron source which makes possible the investigation of unexplored ultrafast processes in manifold fields of research.
Understanding the ultrafast dynamics of materials under extreme conditions is challenging. Here the authors use a femtosecond betatron X-ray source to investigate the solid to dense plasma phase transition in copper using XAS with unprecedented time resolution.