Eur. Phys. J. D (2016) 70: 115
https://doi.org/10.1140/epjd/e2016-60727-3

Regular Article

Autoionization following nanoplasma formation in atomic and molecular clusters^*

¹ Max-Born-Institut, Max-Born-Strasse 2A, 12489 Berlin, Germany
² Department of Physics, Imperial College London, South Kensington Campus, SW7 2 AZ London, UK
³ Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr 36, ER 1-1, 10623 Berlin, Germany
⁴ Lund University, Professorsgatan 1, 22363 Lund, Sweden

^a e-mail: schuette@mbi-berlin.de

Received: 22 December 2015
Received in final form: 27 February 2016
Published online: 19 May 2016

Abstract

Nanoplasmas resulting from the ionization of nano-scale particles by intense laser pulses are typically described by quasiclassical models, where electron emission is understood to take place via thermal processes. Recently, we discovered that, following the interaction of intense near-infrared (NIR) laser pulses with molecular oxygen clusters, electron emission from nanoplasmas can also occur from atomic bound states via autoionization [Schütte et al., Phys. Rev. Lett. 114, 123002 (2015)]. Here we extend these studies and demonstrate that the formation and decay of doubly-excited atoms and ions is a very common phenomenon in nanoplasmas. We report on the observation of autoionization involving spin-orbit excited states in molecular oxygen and carbon dioxide clusters as well as in atomic krypton and xenon clusters ionized by intense NIR pulses, for which we find clear bound-state signatures in the electron kinetic energy spectra. By applying terahertz (THz) streaking, we show that the observed autoionization processes take place on a picosecond to nanosecond timescale after the interaction of the NIR laser pulse with the clusters.