No abstract

We propose a new method to determine magnetic fields, by using the magnetic-field induced electric dipole transition 3p 4 3d 4 D 7/2 → 3p 5 2 P 3/2 in Fe 9+ ions. This ion has a high abundance in astrophysical plasma and is therefore well-suited for direct measurements of even rather weak fields in e.g. solar flares. This transition is induced by an external magnetic field and its rate is proportional to the square of the magnetic field strength. We present theoretical values for what we will label the reduced rate and propose that the critical energy difference between the upper level in this transition and the close to degenerate 3p 4 3d 4 D 5/2 should be measured experimentally since it is required to determine the relative intensity of this magnetic line for different magnetic fields. * Electronic address: Tomas.Brage@fysik.lu.se † Electronic address: rhutton@fudan.edu.cn

Spectroscopy in the wavelength region of 330 nm to 400 nm for highly charged tungsten was performed using the High Temperature Super Conducting Electron Beam Ion Trap (SH-HtscEBIT) at Fudan University. Three lines from palladium-like tungsten (W 28+ ) were identified as transitions between metastable levels in the first excited configuration ([Kr]4d 9 4f). A secondorder relativistic many-body perturbation theory approach and a simple collisional radiative model were used to theoretically study the fine structure levels of the 4d 9 4f configuration. The calculated results show qualitative agreement with experiment. We conclude that some levels in the 4d 9 4f excited configuration have extremely long lifetimes and may exhibit extraordinarily high populations, possibly leading to indirect ionization in, for example, fusion plasmas.