Revised Lifetimes of Energy Levels in Neutral Iron.

Mean radiative lifetimes for 408 energy levels of neutral iron are revised from our 1967 paper on the basis of comparison with 81 subsequently measured lifetimes. The standard deviation of the ratio of the revised values to the reference lifetimes is 30 percent.

Proposed Secondary Wavelength Standards and Line Classifications in Thorium Spectra Between 0.9 and 3 µ m.

The spectrum of thorium as emitted by an electrodeless lamp has been recorded by Connes and collaborators by means of Fourier Transform Spectroscopy in the region 0.9 to 3 µm. Of the 3100 lines observed, about 1900 are classified as transitions in the energy level system of Th i and 412 in Th ii. Since the average deviation between the observed and calculated wave numbers is less than 0.002 cm-1, the observed wavelengths are suitable for use as standard wavelengths.

Infrared Spectra of Cerium (Ce I and Ce II) Between 0.8 and 2.4 µm.

The cerium spectrum emitted by an electrodeless lamp has been observed with a SISAM spectrometer in the region from 0.82 to 2.42 µm. Of the 2076 lines observed, about 1100 lines have been classified as transitions in the energy level system of Ce I and 400 lines in Ce II. The average deviation between the observed wave numbers and those calculated from the two energy levels is ±0.023 cm-1 .

New Even Levels and Classified Lines in the First Spectrum of Tungsten (W i).

Ten new even levels, which classify 161 previously unclassified lines, have heen found in the first spectrum of tungsten. Nine of these fit levels in the (5d + 6s)6 mixture of configurations calculated theoretically by Shadmi and Caspi.

Energy Levels and Classified Lines in the First Spectrum of Technetium (Tc i).

Progress in the classification of Tc i lines is reported. About 2200 of the known Tc i lines between 2154 and 8918 Å are now classified as transitions between 108 even and 147 odd energy levels. Tables of levels and classified lines are given.

The First Spectrum of Tungsten (W i).

The first spectrum of tungsten (W i) has been observed in the region between 2000 Å and 10500 Å. Of the 6800 spectral lines reported here, about 5500 have been classified as transitions between 91 even and 365 odd levels.

An Improved Description of Technetium Spectra (Tc i and Tc ii), 2000 to 9000 Å.

A new description of technetium spectra has been made that is more complete and provides more accurate data on wavelengths than those reported heretofore. The observations were made in the region 2000 to 9000 Å with arc and spark sources. Larger samples of technetium and spectrographs of higher resolution were used and the number of lines reported (4500) is more than doubled. The intensities are estimated over a range from 1 to 20,000 and the relative strengths in arc and spark permit assignment of the origin of the lines to neutral atoms (3300 lines) or ions (1200 lines).

Lifetimes of Energy Levels in Neutral Iron.

Mean radiative lifetimes for 408 energy levels of neutral iron are calculated from the known transition probabilities of 3288 lines of Fe i.

Transition Probabilities in Argon I.

In order to derive transition probabilities from intensity measurements of Ar I lines made by Dieke and Crosswhite, new transition probabilities for 26 lines from high levels in Ar I have been measured in a high current constricted arc. With these data, relative level populations of Ar I in Dieke and Crosswhite's rnicrewave discharge are determined and transition probabilities for 240 lines of Ar I in the wavelength range 4100 to 9800 Å are derived. The new values are compared with other published values.