The quality of solar, stellar, and interstellar observations is now so high that we can see physical effects that have been assumed to be insignificant. In natural isotopic mixtures essentially all atomic lines are asymmetric because of isotopic and hyperfine components. In astrophysics the effects of isotopic components have been generally ignored in the case of Ti, Cr, Fe and Ni. Ignoring isotopic splitting introduces the following systematic errors: (1) the use of bisectors to determine velocity fields is incorrect; (2) Fourier analysis of line profiles to determine rotational, microturbulent, and macroturbulent velocities is incorrect; and (3) damping constants are overestimated. When the stronger components become saturated, the weak components are still on the linear part of the curve of growth. This introduces the additional systematic errors; (4) wavelengths of saturated lines are shifted; and (5) abundances determined from equivalent widths are wrong. In addition the Doppler width and Voigt profile of each isotope are significantly different. It is imperative that laboratory measurements be made to determine the isotopic splitting of every energy level of every stable isotope of every atom and ion as is now routinely done for actinides and for diatomic molecules. Hyperfine splitting should be measured as well for those isotopes with nuclear spin. Russia, the United States, and other countries should stockpile pure stable isotopes so they will be available for these measurements. Computer programs for analyzing spectra including the hyperfine and isotopic splitting already exist. We now need the laboratory data.

Atomic data for interpreting stellar spectra: isotopic and hyperfine data

High resolution Fourier transform spectroscopy with the Imperial College (IC) UV-FT spectrometer, and its applications to astrophysics and atmospheric physics: a review

Fifty seven new electron levels of odd parity in neutral praseodymium are presented. These have been found on the basis of an analysis of hitherto unclassified spectral lines with the method of laser-induced fluorescence (LIF). For all the levels the hyperfine magnetic dipole interaction constants A have been determined.

https://iopscience.iop.org/article/10.1088/0031-8949/74/6/010/pdf

New levels and hyperfine structure evaluation in neutral praseodymium

The study of isotope shifts and hyperfine effects in dielectronic recombination (DR) resonance spectra strikes a conceptually new path for investigations of nuclear properties such as charge radius, spin, magnetic moment of nuclei or lifetimes of long-lived excited nuclear states. A series of DR experiments with heavy three-electron ions (Li-like) was performed at the heavy-ion storage ring ESR of the GSI Helmholtzzentrum fur Schwerionenforschung, Darmstadt, Germany. In a pilot experiment the two stable isotopes A=142 and A=150 of neodymium ANd57+ were investigated. From the displacement of DR resonances the isotope shifts δE142,150(2s – 2Pl/2) = 40.2(3)(6) meV and δE142,150(2s – 2p3/2) = 42.3(12)(20) meV for 2s – 2Pj transitions of the Li-like ions have been obtained. An evaluation within a full QED framework yielded a change in the mean-square charge radius of 142,150δ(r2) = −1.36(1)(3) fm2. At GSI, in addition to stable isotopes, in-flight synthesized radioisotopes can be studied as well. The production of radioisotopes of interest, the subsequent separation in the storage ring ESR and first DR experiments with the exotic nuclei 237U89+ and 234Pa88+ (Z=91) are presented. The paper is concluded with a brief outlook at future DR experiments with heavy radioisotopes at the ESR.

/pdf/isotope-shifts-in-dielectronic-recombination-from-stable-to-3vv0mngjvr.pdf

Isotope shifts in dielectronic recombination: From stable to in-flight-produced nuclei

42 new electron levels in singly ionized praseodymium are presented: 28 low-lying odd levels with f3 core and 14 even levels. These have been found on the basis of an analysis of 61 hitherto unclassified spectral lines with the method of laser induced fluorescence. For all the levels the hyperfine structure constants A and B have been determined.

New Levels and Hyperfine Structure Evaluation in Singly Ionized Praseodymium

Hyperfine structure is common in spectral lines. Hfs splits lines due to nuclear moments and shifts lines of different isotopes (IS). Both effects, even if they are small compared with the line- and instrumental-width, broaden and shift the lines and alter their shape and may lead to erroneous interpretations of spectra of astrophysical interest. The IS permits in principle the observation of isotope abundances (e.g. for H-D) but - if unresolved - shifts lines particularly if intensities are strongly affected by absorption (a fake Doppler shift, especially of interstellar lines). The hfs-splitting and its influence on spectral-lines is investigated with a momentum analysis of the hfs and the line-profile, and of the convolved curve. It is found that the hfs can be misinterpretated as Doppler broadening. In optically dense media (e.g. in stellar interior) hfs and IS may decrease the average transparency. Scaling laws for hfs and IS are given.

H Hühnermann

Papers

Hyperfine structure in stellar spectral lines: a little nothing, a help, or a troublemaker?