Evidence of high-n hollow-ion emission from Si ions pumped by ultraintense x-rays from relativistic laser plasma

¹ Theoretical Division, Los Alamos National Laboratory - Los Alamos, NM 87545, USA
² Institute for Academic Initiatives, Osaka University - Suita, Osaka 565-0871, Japan
³ Joint Institute for High Temperatures, Russian Academy of Sciences - Moscow 125412, Russia
⁴ National Research Nuclear University MEPhI - Moscow, 115409, Russia
⁵ York Plasma Institute, Department of Physics, University of York - York YO10 5DD, UK
⁶ SUPA, Department of Physics, University of Strathclyde - Glasgow G4 ONG, UK
⁷ PPC Osaka University and JST, CREST - 2-1, Yamadaoka, Suita, Osaka 565-0871, Japan
⁸ Central Laser Facility, STFC Rutherford Appleton Laboratory - Didcot, Oxfordshire OX11 0QX, UK
⁹ Max Born Institute - Berlin 12489, Max-Born str. 2a, Berlin, Germany
¹⁰ ELI-ALPS - Szeged H-6720, Hungary
¹¹ Institut für Optik und Quantenelektronic, Friedrich-Schiller-Universität Jena - Max-Wien Platz 1, D-07743 Jena, Germany

Received: 11 March 2016
Accepted: 6 May 2016

Abstract

We report on the first observation of high-n hollow ions (ions having no electrons in the K or L shells) produced in Si targets via pumping by ultra-intense x-ray radiation produced in intense laser-plasma interactions reaching the radiation dominant kinetics regime (RDKR). The existence of these new types of hollow ions in high-energy density plasma has been found via observation of highly resolved x-ray emission spectra of silicon plasma. This has been confirmed by plasma kinetics calculations, underscoring the ability of powerful radiation sources to fully strip electrons from the innermost shells of light atoms. Hollow-ions spectral diagnostics provide a unique opportunity to characterize powerful x-ray radiation of laboratory and astrophysical plasmas. With the use of this technique we provide evidence for the existence of the RDKR via observation of asymmetry in the observed radiation of hollow ions from the front and rear sides of the target.