Vacuum Wavenumber Research Articles

A3Π and B3Σ–excited states of the SO radical. Part 3.—The 0–0 band spectrum of the A3Π1–X3Σ–transition

A frequency-doubled frequency-scanning dye laser has been used to excite ro-vibrationally resolved levels of SO(A3Π1, ν= 0) at ca. 259 nm. The rotationally resolved laser excitation spectrum of the 0–0 band of the SO(A3Π1–X3Σ–) transition is reported here. Rotational assignment of the spectrum is given along with vacuum wavenumbers of the observed lines. The vacuum wavenumber of the band origin was measured to be 38 086.68 ± 0.20 cm–1. A strong vibrational perturbation is observed to affect the ν′= 0 level, causing a downward shift in the 0–0 band origin of 6.10 cm–1, referred to its expected position on the basis of extrapolation from higher levels. The rotational structure of the band appears to be perfectly regular, with rotational constants B′0= 0.606 ± 0.002 cm–1, D′0= 0–16 cm–1. The collision-free lifetime of SO(A3Π1, ν= 0) was determined to be 39.2 ± 3.6 µs.

Generation of continuous-wave 194-nm radiation by sum-frequency mixing in an external ring cavity

Several microwatts of tunable cw radiation near 194 nm in a linewidth of less than 2 MHz have been generated by sum-frequency mixing the radiation from a frequency-doubled argon-ion laser with the radiation from a ring dye laser in a crystal of potassium pentaborate. An external ring cavity resonant with the dye laser gives an enhancement factor of about 14 in the sum-frequency-generated radiation power. The Doppler-limited absorption spectrum of the 6s(2)S((1/2))-6p(2)P((1/2)) first resonance line of natural Hg II has been resolved, and the vacuum wave number for the mass-202 isotope has been measured to be 51485.904(20) cm(-1).

Diffraction in Dispersive Media: A System-theoretical Approach

After a short reminder of system theory, it is shown that polychromatic diffraction in dilute dielectric dispersive media leads to an input-output relationship between field amplitudes incident on and emerging from a spatially modulating transparency. If Rayleigh-Sommerfeld diffraction theory is used and in Green's function the vacuum wavenumber is replaced by a function of susceptibility, which depends on frequency, then the system-theoretical interpretation of the formula is straightforward. Linearity, time-invariance and causality are satisfied and the state space is physically identifiable.

High-resolution analysis of the B3Π(0 +) ← X1Σ + absorption spectrum of BrF

Eighteen bands of the B 3Π(0 +) ← X 1Σ + systems of 79BrF and 81BrF have been photographed at high resolution in the range λ 4770–5700 Å. The vacuum wavenumbers of the rotationally analyzed bands were fitted by least squares. Merged molecular constants were derived for 1 ≤ v′ ≤ 9 of B 3Π(0 +) and for v″ = 1 and v″ = 2 of X 1Σ +, and confirm the ground-state constants obtained from the microwave spectrum. Predissociation is sufficiently strong in the B 3Π(0 +), v′ = 9 level to cause observable line broadening.

Rapid Calculations of Vacuum Wave Numbers

In 1953 Edlen published a paper relating the refractivity of dry air to wavelengths in vacuum. His formula was recommended by the Joint Commission for Spectroscopy. In 1952 he published for the National Research Council of Canada Vacuum Corrections for Wavelengths from 2000 to 13500 A. The tables were useful in the calculations of vacuum wave numbers in ultraviolet and visible spectroscopy. However, in these days of programmable calculators the use of his tables is more cumbersome than need be and it is the purpose of this communication to show how the relationships he used can be adapted to the rapid calculations of vacuum wave numbers from wavelengths in air.

Tables of atomic spectral lines for the 10000 Å to 40000 Å region

This compilation of atomic spectral lines for the 10000 Å to 40000 Å region tabulates 8885 selected lines, belonging to 57 elements, extracted from computer based data records. The tables are divided into three sections. In section I the strong lines in the 10000 Å to 25000 Å range are listed for 27 elements. Section II is a table of classified and unclassified lines, arranged in order of increasing vacuum wavenumber. Section III consists of vacuum wavenumber tables, with appropriate energy level and J values for the classified lines, listed by element. Detailed explanation of the data and sources used for the compilation are given.

An infrared atomic wavenumber library

An infrared atomic vacuum wavenumber library, covering the range 10,000–2500 cm −1, has been developed. At the present time 12,827 wavenumbers of 56 elements are stored and, as further information is published, the new data is added to the library. A wavenumber search program has been developed to help in the identification of impurity lines which may appear in a recorded infrared atomic spectrum.

The A2Σ +- X2Π i electronic band system of the OD free radical : Spectroscopic data for the 0-0 sequence, and rotational term values for A2Σ + and X2Π i

The A 2Σ +- X 2Π i emission system of the OD radical has been recorded at high resolution from a discharge through flowing D 2O at 0.1 torr pressure. The 0-0, 1-1, and 2-2 bands of the Δ v = 0 sequence have been analyzed in detail for the first time. A table of the vacuum wavenumbers and wavelengths in air of the rotational lines of these bands is presented, together with some additional measurements for the 0–1 band. The data are used to obtain a self-consistent set of term values for v′ and v″ = 0, 1, which reproduces the observed line frequencies with an average deviation of less than 0.02 cm −1. Earlier, lower resolution data for bands with v′ and v″ = 2, 3 are also combined with the present measurements to give approximate term values for these higher levels.

The Refractive Index of Air

Present knowledge of the refractive index of air is reviewed. Regarding the absolute values there are as yet no definite indications that the standard adopted in 1953 on the basis of Barrell and Sears' measurements should be changed, but new experiments aiming at reducing the present uncertainty of about ± 5 × 10-8 would be desirable.Several recent investigations have contributed important new information on the dispersion of air, which has made it possible to derive an improved dispersion formula for standard air, (n − 1)s × 108 = 8342.13 + 2406030 (130 − σ2)-1 + 15997 (38.9 − σ2)−1, where σ is the vacuum wave-number in μm-1. The deviations from the 1953 formula are small and practically negligible in most spectroscopic work.An equation for the dependence of refractivity on temperature and pressure based on theoretical considerations has been derived. For the range of atmospheric conditions normally found in a laboratory the equation can be approximated by the formula (n − 1)tp = (n − 1)s × 0.00138823 p/(1 + 0.003671 t), with p in torr, t in °C, and (n − 1)s given by the dispersion formula for standard air.The effect of carbon dioxide and water vapour is discussed. From Erickson's dispersion data for water vapour, combined with Barrell and Sears' absolute measurements, one obtains the equation ntpf – ntp = −f (5.722 − 0.0457 σ2) × 10-8 for the difference in refractive index of moist air, containing f torr of water vapour, and dry air at equal temperature and total pressure. The equation is valid for visible radiations and normal atmospheric conditions.

Rotational and vibration constants of CO

The spectrum of CO has been observed using a heated absorption tube. J values up to 48 for the 2-0 band and up to ∼35 for the 3-1 and 4-2 bands were measured. Using previous measurements of the 2-0 band and the results of microwave determinations a set of rotation-vibration constants was deduced. The vibrational constants in vacuum wave numbers are: W e = 2169.8232, W eX e = -13.2932, W eY e= 0.01144. The rotational constants are: B 0 = 1.922 521, D 0 = −6.1193 × 10 −6, H 0 = 5.8 × 10 −12, α e = −0.017507, β e = 1.0 × 10 −9, γ e = 1.0 × 10 −6. Calculated values for lines in the 5-3, 6-4, and 7-5 bands agree within experimental error with the results of measurement of lines in the solar spectrum.

Wavelength Calibrations in the Infrared IV Use of a 1000-Lines-per-Inch Bausch and Lomb Plane Replica Grating

It has been demonstrated that the 1000-lines-per-inch Bausch and Lomb plane replica grating can be employed for high-resolution infrared studies anywhere in the region between 1 and 40 μ. In this manner, calibration procedures become simplified in measuring wavelengths relative to the CO standards. A map of the pure rotational lines of the H2O molecule along with the vacuum wave numbers of these lines has been presented.

Investigation of the Invariance of Atmospheric Dispersion with a Long-Path Refractometer*

An investigation has been made of the extent to which the relative refractivity of the atmosphere is invariant under changes in pressure and humidity. To achieve the necessary precision a refractometer with double-passed chambers 14.3 m long was designed for use in the photographic region. No fiducial line is employed. The relative refractivity of dry air was found to vary by less than 3 × 10−6 over the region from 3890 to 6440 A for a change in pressure of 12 atm. The relative refractivity of water vapor at low pressure in the region from 3610 to 6440 A was found to be δ˜H2O=0.961646+0.0086062k2−0.00010547k2+0.00001312k6,where k is the vacuum wave number in μ−1.

Wavenumber Reproducibility of the Radiation 2p10?5d5 of Krypton 86

The vacuum wavenumber of the radiation 2PlO-5d5 (6056 A) of krypton 86 emitted by a hot cathode Engelhard-type discharge lamp has been established for the temperature range 58-70 oK and current density range 0-1' 0 A/cm'. Wavenumbers relative to the value for the unperturbed state of the radiation have been measured with a reliability of 1 part in 109 using a photoelectric recording and electromechanical scanning FabryPerot interferometer. However, this reproducibility is not possible for different lamps without a more exact specification for the form and operation of the lamp and for the interferometric system used. With the present international specification for the lamp, the reproducibility of this new primary standard of length is better than 1 part in 108.

Rapid Precision Wave Number Measurements from Fabry-Perot Interferograms*

In order to obtain the more accurate wave numbers needed for studies of the very rich heavy element spectra, a new measuring and calculating procedure has been developed. A modern sharp line source, such as a hollow cathode discharge or an electrodeless metal-halide lamp, is used to illuminate a vacuum Fabry-Perot interferometer (5, 10, or 20 mm spacer). The interferometer is crossed with a spectrograph resolving the free spectral range of the interferometer. The resulting interferogram is measured with a two-coordinate photoelectric comparator. The measurements are punched on IBM cards, and vacuum wave numbers are directly calculated with a high-speed digital computer. Only one standard line is needed and the index of refraction of air correction is used only to obtain air wavelengths. The phase change correction is obtained from measurements with two different spacers or from measurements on several standard lines. Only a few minutes reading time are needed for each line. This procedure is being used for a further study of the uranium spectrum with sources containing separated uranium isotopes. Over 8000 lines near 4100 A have been measured with a precision better than 0.005 cm−1.

The Application of Digital Computers to the Reduction and Analysis of High-Dispersion Molecular Spectra.

view Abstract Citations (10) References (3) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Application of Digital Computers to the Reduction and Analysis of High-Dispersion Molecular Spectra. Phillips, John G. Abstract Programs have been developed for the IBM 701 digital computer for the calculation of vacuum wave numbers from line measurements and for the identification of the branches into which the lines of individual bands may be divided. Tests on representative spectra show that great savings of time and labor may be achieved, especially if the programs are used in conjunction with digitizing equipment on the measuring machines to punch the measurements directly onto IBM cards. Publication: The Astrophysical Journal Pub Date: July 1959 DOI: 10.1086/146718 Bibcode: 1959ApJ...130..308P full text sources ADS |

Hyperfine structures of the resonance lines of indium 115

Spectroscopic measurements reported in an earlier paper are converted to vacuum wave numbers to give a true comparison with microwave measurements.

Analysis of Atomic Spectra with Electronic Digital Computers

A method has been developed for the analysis of atomic spectra with high speed electronic digital computers. The conversion of wavelength in air to vacuum wave numbers, the search for spectral terms, and the construction of square arrays are performed by machine computation. These techniques are applied to the analysis of the arc spectrum of ruthenium.

Energy Levels and Wavelengths of Natural Cadmium and of Cadmium-114

In the region 8200–2144 A the wavelengths or vacuum wave-numbers of seventy-three lines in the first spectrum and eleven in the second spectrum of cadmium have been measured relative to neon standards or to the mercury-198 spectrum or to both. The source for natural cadmium was a Beese lamp operated at 2.5–4.5 amp. For cadmium-114 the source was either a quartz Michelson lamp (plus 1.0 mm argon) operated under standard conditions or at lower temperature, or an electrodeless tube containing 0.5 mg of cadmium-114, 0.5 mg of mercury-198, and neon at 3 mm pressure. The use of cadmium-114 is preferable if the lines arising from S−P combinations are to be used as secondary standards. For P−D combinations the natural element is quite satisfactory. The characteristics of various sources are discussed. For the greater part of the observation required for this publication we have used the interferometer in vacuum; wave numbers so observed are unaffected by the refractive index of air and its changes with temperature, pressure, and constitution.The vacuum interferometer and Michelson lamp were described in another paper by Kenneth B. Adams and Keivin Burns. [ K. B. Adams K. Burns , J. Opt. Soc. Am.46, 36 ( 1956)].The wave numbers of mercury-198 measured by means of the vacuum interferometer have been compared with the wavelengths measured in air and converted to wave numbers by Edlen’s formula [ Transactions of the Joint Commission for Spectroscopy, J. Opt. Soc. Am.43, 412 ( 1953)]. From 5790 to 2636 A the relative accuracy of the formula is confirmed. By differences in cadmium wave numbers the formula is checked from 6438 to 2288 A. Edlen’s formula is used throughout this paper wherever wavelengths in air are converted to wave numbers in vacuum or vice versa.

The Dispersion of Standard Air*

By combining Barrell and Sears’ measurements in the visible and Koch’s and Traub’s in the ultraviolet, a dispersion formula for standard air has been derived, viz., (n−1)108=6432.8+2 949 810(146−σ2)−1+25 540(41−σ2)−1,σ being vacuum wave number in μ−1, which should satisfy all needs of precision spectroscopy, in particular for converting wavelengths in air into vacuum values.

The Dispersion of Air Between 2500A and 6500A

The available experimental data on the optical dispersion of air have recently been critically assessed by Meggers and Kessler. They find that none is satisfactorily reliable when subjected to a test depending upon the application of the Ritz combination principle to term analysis in the first spectrum of 19880Hg lying between 2536A and 5791A. In the present paper, a new dispersion curve for air is derived from reasonably concordant refractivity data previously obtained in the visible spectrum at three different laboratories. The cauchy equation of this curve is used to reduce to vacuum wave numbers the highly precise wavelengths in air of 27 lines of 19880Hg measured by Meggers and Kessler. If the truth of the combination principle is assumed, the constancy of recurring term intervals between 2536A and 5791A shows that the new dispersion equation for air is at least as reliable as the original wavelength measurements, for which an average accuracy of ±0.0001A was claimed. Alternative forms of the general refractivity—density relationship are quoted which render the new dispersion equation suitable for practical use in spectroscopy and length metrology.