Proposal for observation of transitions induced by external magnetic fields mixing in the lower states: with an example from Fe X

Abstract

It is normally assumed that induced transitions, by e.g. hyperfine, magnetic field or spin interaction, arise due to mixing in the upper levels. In this paper we discuss an example when mixing in the lower levels through an externally applied magnetic field gives rise to a magnetic field induced transition. We discuss the theory for such a transition and give an example from Fe X, which is relevant for the determination of the magnetic field of the solar corona. To make this possible, it is important to determine the energy difference between the 3p43d 4D5/2 and 4D7/2, which are accidentally very close in energy in Fe X. The splitting of these levels is expected to be around 3.5 cm−1 whereas their excitation energies are about 388 709 cm−1. We discuss how this fine structure can be determined, by observing transitions from levels that decay into this pair which have a longer wavelength than the resonance transition. Finally we discuss an experimental scenario based on an electron beam ion trap and a Fabry–Perot interferometer, to perform the measurement of this interval.

Hinode/EIS measurements of active region magnetic fields

“…The first and most important is the intrinsic uncertainty in the calculation of the Einstein coefficient A M IT for the magnetically-induced transition. As discussed by Si et al (2020a), to first order we can assume…”

“…Recently, Li et al (2015Li et al ( , 2016 and Si et al (2020a) reported on a peculiar atomic physics configuration which makes the wavefunction composition of a low-energy metastable atomic level of Fe x sensitive to the presence of an external magnetic field. This sensitivity would remain a curious feature of a single, metastable Fe x, if this level didn't happen to significantly contribute to the emission of one of the strongest lines in the Fe x spectrum in the solar corona at 257.26 Å.…”

Absorption spectroscopy and Stokes polarimetry in a $^{87}$Rb vapour in the Voigt geometry with a 1.5 T external magnetic field

“…Applications of such atomic sensors span a variety of disciplines, ranging from explosives detection [11]; gyroscopes [12]; medical imaging of soft tissues [13][14][15][16]; microfluidics [17] and measurements on spin-active solidstate systems [18]. In order to improve and sustain the development of these technologies, atomic spectroscopy in the presence of external magnetic fields has become an area of wide interest [19][20][21][22][23]. This in turn has given rise to a variety of experiments and optical devices [24][25][26][27][28][29][30][31] that help demonstrate the depth of understanding of the physics involved in said interactions, furthering the reach and possible applications of this area.…”

A first spectroscopic measurement of the magnetic field strength for an active region of the solar corona

“…To address this, we have over the past few years been investigating a spectroscopic method based on quantuminterference effects in the Fe 9+ ion (Li et al 2015(Li et al , 2016Judge et al 2016;Si et al 2020). This particular interference is caused by magnetic fields external to the ion, and hence this idea has the potential to act as a probe of the coronal field strengths.…”

“…A search for an atomic system involving a suitable pseduo-degeneracy was initiated a few years ago (Li et al 2015(Li et al , 2016Judge et al 2016;Si et al 2020), motivated by its potential as a magnetic-field probe. This led to the discovery of Fe 9+ where the excited levels 3p 4 3d 4 D 5/2 and 4 D 7/2 fulfill the requirements of being very close in energy and having significantly different lifetimes.…”