Curtis J. Humphreys

Accurate Energy Levels and Calculated Wavelengths of 86 Kr i

A total of about 240 spectral lines of 86Kr i has been measured interferometrically during the past decade. Some have been measured in only one laboratory while others have been measured in as many as 12. On the whole, the agreement is good, but some discrepancies appear. For this work, almost all of the wavelengths have been averaged and used for the determination of a best set of energy-level values for this isotope of krypton. Forty-five even and 66 odd levels have been calculated by the method of least squares, with uncertainties ranging from ±0.0001 to ±0.0016 cm−1 These interferometrically determined levels have, in turn, been used to calculate a completely consistent set of wavelengths that are preferable to any single set of measurements or averages of measurements of 86Kr i. The list of 530 lines contains only those calculable transitions that have been observed from krypton sources in the spectral region 3300–40 700 A. With the exception of a number of weak lines and some close pairs, the final list of wavelengths is recommended for consideration for adoption as secondary standards.

Interferometric Wavelength Determinations in the First Spectrum of 136 Xe

Interferometric wavelength determinations in the first spectrum of 131Xe, covering the photographically observable region between 3949 and 11 088 A, and the nonphotographic region between 12 626 and 35 079 A, are reported. Photographic intercomparisons were made with I.A.U.-recommended standards of 198Hg at 4047 and 4359 A. Study of the properties of several ir lines of Ar i led to the adoption of the line of wavelength (in air), 16 940 A, as the most suitable standard for the radiometric intercomparisons. Wavelengths of a total of 221 lines are reported, including 15 between 12 626 and 35 070 A. Energy levels have been determined to the extent permitted by the interferometric observations. All material on this spectrum presented at recent meetings of the Optical Society of America, or contained in internal reports, is included.

First Spectrum of Chlorine; an Extension Based on Observations in the 7000 to 25 000 A Region*†

The spectrum of neutral chlorine excited by means of a Raytheon Microtherm unit in electrodeless tubes filled with the pure gas has been observed in the region between 10 000 and 25 000 A. A description has been prepared giving wavelengths, wave numbers, and relative intensities of 283 radiometrically observed lines. Newly classified lines selected from a recent set of photographic observations by Corliss in the interval between 7000 and 10 000 A are included. Extensions to the established classification include identification of all 22 of the previously unobserved levels of the family associated with the 3P ion limit, comprising the levels from the 3s23p45s and 3s23p43d configuration. From a study of this material, along with his list of wave numbers, Corliss has found fourteen new odd levels. Further systematic combing of the data by use of an automatic computing program has revealed four additional odd levels. The new odd levels originate probably in the 3s23p44f configuration.

The First Spectrum of Mercury in the Region between 1.3 and 2.0μ

The spectrum of neutral mercury has been observed in the region between 1 and 2.0μ, with a high-resolution grating spectrometer employing a lead sulfide detector. A noteworthy feature of the new observations is the essentially complete resolution of the D-F multiplets involving both first and second members of F series. Such resolution was achieved only with a low-pressure source. All new lines have been classified. A few changes in existing classifications and minor revisions in term values are suggested.

Spectra of the Noble Gases in the 4-μ Region*

The spectra of neon, argon, krypton, and xenon have been observed in the wavelength region 3.8 to 4.1 μ, using an infrared spectrometer equipped with cooled lead sulfide detector. The most important observations are of the near-hydrogenic and closely pair-coupled 4f–5g transitions, which establish for the first time all the 5g level pairs lying below the first ionization limit of each element. A detailed investigation of the theoretically predicted 4f–5g energy levels and relative line strengths shows very good agreement with observation. Various p–s, p–d, and d–f transitions have been identified, the most significant new result being the establishment of the level pairs 5f[412]4,5 and 5f[312]3,4 of Ne i, which previously had been only estimated.

Interferometric Observations in the Spectra of 86 Kr

Wavelengths in the first and second spectra of 86Kr are reported. Included are results of observations in the nonphotographic infrared region and conventional intercomparisons by use of Fabry-Perot interferometers in a vacuum, with the primary wavelength standard at 6057 A, originating in a microwave-excited electrodeless discharge operated at the triple point of nitrogen. The wavelengths are in the region between 3623 and 28 663 A. All wavelengths of these spectra that have been reported at recent meetings of the Optical Society of America or in internal reports are included.

Extension of Observations and Analysis of Ge i

An investigation of the extra-photographic infrared region of Ge i utilizing electrodeless discharge tubes containing germanium tetraiodide, a grating spectrometer, and a lead sulfide detector has yielded 117 lines, observed between 11 252 and 23 922 A. Subsequent interferometric determinations of 30 lines between 11 252 and 19 284 A were carried out by scanning the circular fringes of a Fabry–Perot interferometer across the spectrometer slit to achieve accuracies of from 0.001 to 0.003 A in this region. The motivation for this investigation came from the knowledge that the solution of difficulties which Andrew and Meissner [ J. Opt. Soc. Am.49, 146 ( 1959)] encountered in establishing the levels of the 4s2 4p nf configurations of Ge i lay in the extra-photographic infrared. Of the 12 levels belonging to the 4p4f configuration they established only two by as much as a single pair of transitions; leaning heavily on the theory, they identified five others by a single transition each and predicted the positions of the remaining five. This investigation confirmed the tentative levels and established the missing levels which were found to lie close to their calculated positions. Similarly, values of 4d3F4, 5f, 6f, and 7f3G5, previously estimated by Andrew and Meissner with an uncertainty of ±5 cm−1, were verified and established to within ±0.1 cm−1. New values for the 6p3D3 and 6p1S0 levels were obtained. Also included are photographic grating measurements of a number of the weaker lines of Ge i not previously observed in the wavelength range 5006–10 858 A which were obtained from 12 to 14 h exposures with electrodeless discharge tubes containing germanium oxide and neon.

The Observation of Extraphotographic Infrared Atomic Emission Spectra

The extension of observation of atomic line emission spectra into the extraphotographic infrared region by high-resolution methods has been accomplished by procedures now well established but which have not found widespread application. Owing to the nonintegrating character of radiometric detecting devices, the observations are always energy-limited. This handicap may be overcome by a threefold approach: utilization of a fast optical system; optimizing the detecting and amplifying system; and developing sources of maximum energy output consistent with the character of the spectrum to be studied. Successful systems for use with a high-resolution grating spectrometer are described. Examples are given of the extension of the observation of several spectra to a fairly easily attainable limit of 4 μ by use of lead sulfide detectors designed for liquid nitrogen cooling.

Progress of Radiometric Observation of Infrared Atomic Emission Spectra

The radiometric observation of infrared atomic spectra during the past half-century may be divided into three periods. During the first, relatively short period of point-by-point observation, associated with Paschen, the thermal detector and astatic galvanometer were brought to a high state of perfection. The infrared spectra of alkalis and alkaline earths were explored in this manner. The following 35 years were unproductive in this field of research. A few excellent investigations took advantage of improved devices such as the thermal relay and automatic recording. During the 10 years of the modern period, photoconductive detectors have been incorporated into scanning spectrometers to permit high-resolution observations in the region beyond the limit of photographic response. This article gives an account of new work since 1956. Details of earlier work are covered in previous reports. The status of infrared observations is summarized and completely referenced. An account of current programs for establishment of standards is included.

Interferometric Measurement of Wavelengths of Infrared Atomic Emission Lines in the Extraphotographic Region

A considerable extension of the international system of wavelength standards has been achieved by direct interferometric intercomparison of accepted standards with selected infrared lines in the region beyond the limit of photographic response. A radiometric system employed successfully for this purpose scans the pattern of Fabry–Perot fringes projected upon the slit of a spectrometer. By tilting the interferometer in uniform angular motion about a vertical axis, a diametral section of the fringe system moves across the slit, generating a set of maxima that are registered on a uniformly moving record chart with the same distribution as that of the fringe diameters. Items discussed include achromatic projection, vacuum techniques, and procedures for the reduction of data.