J. Rand McNally

A Hollow Cathode Source Applicable to Spectrographic Analysis for the Halogens and Gases

Investigations aimed at developing methods of spectrographic quantitative analysis of the halogens and non-metals have been carried out, with emphasis on analysis for fluorine. The relative sensitivities of fluorine spectrum lines in the vacuum ultraviolet region and in the visible region were studied, and it was found that certain visible lines are, at present, more sensitive than the theoretical raies ultimes of fluorine. The greatest absolute sensitivity obtained, using a specially designed hollow cathode source, involved detection of about 0.01 microgram of fluorine, while the greatest concentrational sensitivity was slightly less than one part per million. Chlorine and sulphur were readily detected in amounts as small as 0.20 microgram and 1.0 microgram, respectively, in samples weighing 20 milligrams. Sample handling time was reduced sufficiently to permit routine analyses for these elements.

First Spark Spectrum of Thorium—Classification and Zeeman Effect Data of Th II

Five sets of exposures to the thorium arc in silver, burning in a Bitter electromagnet at fields up to 93,000 oersteds, have given resolved Zeeman patterns for more than 800 lines of Th II. Data obtained from these plates, measured with an automatic comparator and used in connection with improved wave-length measurements, have made possible classification of 1091 lines of Th II as arising from 219 levels. These levels belong to two groups of terms between which no combinations have been found. Group A contains even terms arising from d2s (with a4F112 lying lowest), from d3, and from ds2, and odd terms from d2p, dsp, and fds. About half of all terms expected from these configurations have lceen identified. Group B contains odd terms expected from fs2 (with a2F°212 lying lowest), and fds, and even terms from fsp and fdp. g values are given for all levels, in many cases to within 0.002 unit, which makes available a large amount of fairly exact experimental data for evaluation of perturbations. Partial tests of the g sum rule show good agreement with theory, though all terms are not yet available for inclusion. Perturbations of even those terms which lie low are rather large.

Zeeman Effect Data for the Spectra of Lanthanum—La I and La II

Zeeman effect data are given for 152 lines of La I and 506 lines of La II in the wave-length range 2257A to 7484A. Spectrograms were made at fields of 81,230, 83,370, and 86,570 oersteds using a Bitter electromagnet, and the 24 plates obtained with three diffraction gratings operating simultaneously were measured with an automatic comparator. g values are given for almost all of the classified terms of La I and La II, and the determinations from various lines agree usually to within 0.004 g unit. This makes available an array of unusually precise data for the evaluation of perturbations in typical rich two-electron and three-electron spectra. The g-sum rule of Pauli is verified in a number of cases to within a few tenths of a percent.

First Spark Spectrum of Thorium—Infra-Red Spectrum and Further Classification of Th II*

Investigations of the infra-red spectra of thorium were undertaken in order to establish a correlation between the two previously established but unconnected energy groups in the Th II term structure. Specially sensitized infra-red plates were exposed in a thirty-five foot Wadsworth stigmatic grating spectrograph to sparks between metallic thorium rods and to high current arcs of thoria in carbon and copper electrodes. Many strong arc and spark lines were recorded in the region λ8665A to λ11230A. The desired combination lines were observed and readily established the correlation between the two previously distinct groups of levels. The separation of the low levels D2112 (from 6d7s2) and F2°212 (from 5f7s2) was found to be only 4490.29 cm−1. Infra-red quartet multiplets as well as quartet multiplets involving the most sensitive lines of Th II are presented and discussed. Tables of infra-red wave-lengths and of spectral terms are given in detail.

Zeeman Effects in the Arc, First Spark, and Second Spark Spectra of Yttrium

Exposures to the yttrium arc in silver, burned in the Bitter electromagnet at fields of 85,000 oersteds, yielded interpretable Zeeman effects of the first three spectra of yttrium—Yt I, Yt II, Yt III. Zeeman patterns arising from transitions between energy states of the doubly-ionized atom were observed in the range 2950–2360A. Lande g factors were calculated for the 4d, 5s, and 5p energy levels. Magnetic splitting of lines in the first spark spectrum of yttrium permitted the determination of g values for 59 of the 61 known energy levels. Zeeman effects of the arc lines of yttrium were observed for lines of high intensity only. Inclusion of data of B. E. Moore and of W. F. Meggers gave fairly complete information of the Zeeman effects of Yt I. Over-all g sums pertaining to the singly-ionized atom verify the g-sum rule exceptionally well in spite of large variations of individual g values from the theoretical Ls values. Term classifications were verified in the majority of cases.

High Members of the Principal Series in Caesium

The results of an investigation initiated several years ago are presented in summary form. The more intense doublet member of the principal series of caesium in absorption is recorded sixty-second quantum state, whereas the weaker doublet member is recorded to the to the quantum state only. An empirical formula fitting the longer series to about ±0.03 fourteenth cm−1 is given. The calculated series limit of 31406.32 cm−1 corresponds to an ionization potential of 3.8929 volts for the caesium atom.