Charlotte E. Moore

XUV spectrum of C I observed from Skylab during a solar flare

An intense spectrum of Ci in the wavelength region from 1100 to 2000 A has been recorded by the Naval Research Laboratory normal incidence spectrograph flown on Skylab. The source of the spectrum was a large solar flare. The spectral resolution was about 20000 at 1200 A. We have identified 69 new lines of Ci, and determined 63 new energy levels. The new lines arise from transitions from upper levels of high principal quantum number n where n ≳ 6. A list of 193 Ci lines observed in the spectrum between 1140 and 1931 A is presented, as well as calculated wavelengths for an additional 109 transitions between the new levels and the 2s2 2p2 3P0,1,2 levels. The calculated lines fall between 1102 and 1140 A and were not observed in the solar flare spectrum due to low instrumental efficiency at these wavelengths. The relative wavelength accuracy of most of the observed and calculated lines is about ±0.004 A. The intensities of the C i lines are qualitatively compared with corresponding intensities in the laboratory spectrum.

THE ATOMIC SPECTRA OF THE RARE EARTHS: THEIR PRESENCE IN THE SUN

A summary of the present state of analysis of the first and second spectra of the rare-earth elements is presented with an extensive bibliography. The astrophysical importance of these spectra is stressed. Counts are given of the number of lines of each rare-earth spectrum identified at present in the accessible solar spectrum. Most of them appear only in the singly ionized state; exceptions are Eu i, Tm i?, and Yb i. The possible presence of the strongest laboratory line of Ce iii in the solar spectrum is suggested. If correct, this is the first evidence of a third spectrum line in the accessible range of the solar spectrum (λ > 3000 A).

Ultraviolet solar identifications based on extended absorption series observed in the laboratory spectrum of Sii

The absorption spectrum of Sii in the wavelength region 1500–1900 Å has been photographed at high resolution. The silicon vapour was produced in a 122 cm long King furnace at 1800–2300°C. Forty-two Rydberg series have been observed from the ground state terms 3p23P and1D to terms associated with the 3pns and 3pnd configurations. All of the series from these configurations withJ<4 have been extended with the 3pnd3D3o levels reachingn=56. Numerous perturbations have been observed. This laboratory work has provided the basis for extending the identification of silicon lines in the solar spectrum. Nearly all lines found in the laboratory spectrum are also found in rocket spectrograms of the solar chromosphere. More than 300 lines have been attributed to Sii. The excellent correlation between laboratory and solar Sii lines will be illustrated.

The presence of Si I series in the ultraviolet solar spectrum - 3000 to 1200 A

Laboratory and solar data are presented which form the basis for identifying chromospheric Si I absorption lines in UV rocket spectra of the solar limb. Prints of the Si I laboratory spectrum between 1520 and 1570 A are matched with those of the chromospheric spectrum, and a striking line-to-line coincidence is observed. Individual absorption series of Si I covering the 3p(2), 3P, 1D, and 1S ground terms are tabulated in multiplet form over the wavelength range from 1517 to 3069 A. It is noted that many of the solar lines are blended with both other Si I lines and lines of other spectra.

Atomic spectra—Their rôle in astrophysics

Abstract This paper deals with the use of atomic spectra as a connecting link between stars and atoms, illustrated by the spectrum of the Sun, our nearest star. The importance of the multiplets found from the analyses of laboratory spectra, in the identification of solar lines is exemplified by selected lines of P i , S i , Si i , Mg i , and Fe i . Solar lines identified from predicted wavelengths, calculated from the energy levels, are found among these spectra. The elements represented in the Sun only in compounds or by only one atomic line are discussed in some detail. A second revision of Rowlands Table of Solar Spectrum Wavelengths, including measured equivalent widths and revised identifications, provides an excellent example of the role of atomic spectra in astrophysics.

Infrared Multiplets and the Solar Spectrum

The identification of solar lines in the photographic infrared region is discussed. Sample multiplets of C i, N i, O i, Na i, Al i, Si i, Ti i, and Fe i are listed to illustrate the consistency of term intervals within multiplets, when solar wave numbers are substituted for laboratory values. These data furnish an excellent criterion of both the precision of the solar data and the correctness of the assigned identifications. Solar lines produced by more than one contributor, i.e., blends, can be detected by irregularities in the solar term intervals within multiplets.

Silicon in the sun

Abstract A brief survey is given of silicon lines in the spectra of the solar photosphere, chromosphere and corona. These lines arise not only from the spectrum of the neutral atom, but also from the ionic spectra of every stage of ionization, i.e. Si i through Si xiv . The ionization potentials range from 8 to 2673 eV, and the wavelengths of the solar identifications span the interval from 6 A to 25129 A. The wide range of excitation and ionization thus represented makes silicon a suitable element for detailed study of solar models, fluxes, abundances and the like.