Systematic Observation of EUV Spectra from Highly Charged Lanthanide Ions in the Large Helical Device

Chihiro Suzuki,Shigeru Sudo,Naoki Tamura,Fumihiro Koike,Izumi Murakami

doi:10.3390/atoms6020024

Abstract

We have systematically observed extreme ultraviolet (EUV) spectra from highly charged ions of nine lanthanide elements with atomic numbers from 60–70 in optically thin plasmas produced in the Large Helical Device (LHD). Discrete spectral features with isolated lines from relatively higher charge states around Cu-like ions are observed under high temperature conditions around 2 keV, while narrowed quasicontinuum features from charge states around Ag-like ions are observed under low temperature conditions below 1 keV. The positions of the lines and the quasicontinuum features systematically move to shorter wavelengths as the atomic number increases. The wavelengths of the main peaks in the quasicontinuum features agree well with those of singlet transitions of Pd-like ions reported previously. We have easily identified discrete spectral lines from Cu-like and Ag-like ions, some of which are experimentally identified for the first time in the LHD. Their wavelengths are compared with theoretical calculations using a GRASP family of atomic codes. The theoretical values are synthesized to the LHD experimental data for the cases of Ag- and Pd-like ions.

Highlights

It is well known that bright emission spectra from highly charged ions of lanthanide elements (Z = 57–71) appear in the extreme ultraviolet (EUV) or soft X-ray wavelength range [1,2]
We describe the details of a series of EUV spectra observed in the Large Helical Device (LHD) for the elements with atomic numbers Z = 60–70 in terms of Z dependence
The wavelengths observed in the present study (LHD) are listed with those in the previous experiments and those calculated with GRASP92 and RATIP

Summary

Introduction

Zeng et al [2] recorded a similar series of spectra for the elements with atomic numbers Z = 57–82 using a microchannel plate detector In these studies, quasicontinuum band emissions, the so-called unresolved transition array (UTA) [12], originating from ion stages with 4d and 4f outermost electrons have been observed with fewer isolated lines. Reader and Luther [13,14] observed the spectra of some of the lanthanide elements using a high-energy laser-produced plasma, which resulted in the identifications of some isolated lines of the n = 4–4 transitions of highly charged Cu-like ions. For the cases of Ag-like and Pd-like ions, we have fitted the theoretical values to the LHD experiments and have obtained a set of synthesized spectral wavelengths that are predictable for all the lanthanide elements

Experimental

Theoretical Calculation

Z Dependence of the Spectra

Wavelengths of the Lines from Simple Ions

Findings

Summary