Low-density laboratory spectra near the He ii λ304 line^⋆

¹ Physics Division, Physical and Life SciencesLawrence Livermore National Laboratory, Livermore, CA, 94550-9234 USA
e-mail: traebert@astro.rub.de; beiersdorfer1@llnl.gov
² Astronomisches Institut, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, 44780 Bochum, Germany
³ Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA

Received: 24 November 2015
Accepted: 31 December 2015

Abstract

Aims. To interpret the EUV spectra of the solar corona, one hopes for laboratory data of specific chemical elements obtained under coronal conditions.

Methods. EUV spectra of He, C, N, O, F, Ne, S, Ar, Fe, and Ni in a 40 Å wide wavelength interval near λ304 were excited in an electron beam ion trap.

Results. We observe some two hundred lines about half of which are not yet identified and included in spectral models.

Conclusions. Our data provide a check on the atomic data bases underlying the spectral models that are used to interpret solar corona data. However, a multitude of mostly weak additional lines taken together represent a flux that is comparable to that of various primary lines.