Interferometric Wavelength Measurements Research Articles

Determination of the xenon 6s[3/2]_2–6s′[1/2]_0 clock frequency by interferometric wavelength measurements

We have determined the wave number of the optical two-photon clock transition 6s[3/2](2)-6s'[1/2](0) in xenon by interferometrically comparing the wavelengths of the 6s[3/2](2)-6p'[1/2](1) (lambda = 450 nm) and 6s'[(1/2)] (0)-6p'([1/2]) (lambda = 764 nm) transitions with an iodine-stabilized 633-nm He-Ne laser. These measurements determine the frequency of the two-photon transition [4564.610902(13) cm(-1) for (132)Xe] to better than 1 MHz and provide precise values for the isotope shifts and the hyperfine structures of these transitions.

Interferometric Wavelength Measurements through Post-Detection Signal Processing

Modern electronic signal processing techniques make it possible to use a conventional scanning Fabry-Perot interferometer for highly accurate measurement of (tunable) laser wavelengths. An experimental device is described in which the time intervals between resonances of an unknown wavelength are compared with those of a stabilized He-Ne reference laser by the use of highly accurate electronic timing devices. The accuracy is further enhanced through signal averaging over many scan periods. Accuracies approaching one part in 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> are expected to be readily achievable.

Interferometric wavelength measurements in the infra-red spectrum of isotope xenon 136

A reflecting echelon has been used to determine vacuum wavelengths of 15 isotope xenon 136 spectral lines in the region 0.8-2.6 mu m with a precision of 1 in 107. From these a further 16 wavelengths have been calculated extending to nearby 3.7 mu m. The measurements support the values already published by Humphreys and Paul (1970).

Interferometric wavelength measurements in the spectrum of argon between 1 and 2 μm

The wavelengths of thirteen intense lines in the infra-red spectrum of argon have been measured with a reflecting echelon interferometer by comparison with the primary standard line of krypton 86, to an accuracy of about 0.001 Å. The values of some of the 3 d and 2 s levels of argon have been determined from the measurements and used to calculate the wavelengths of 67 additional lines in the region between 1 and 2 μ m.

Improved Cu ii Standard Wavelengths in the Vacuum Ultraviolet*

Interferometric wavelength measurements of sixty-one copper spark lines in the region 2884 A to 1979 A have been carried out by means of a Fabry-Perot interferometer equipped with 4, 12, and 20 mm spacers. The light source used was a water-cooled hollow cathode Schuler tube operated principally with circulating helium but occasionally with circulating neon.The measurements were employed to establish the 4s and 5s even levels and 4p odd levels of Cu ii. After fixing these low levels, their values were combined with the grating measurements of Carter and Shenstone to establish the values of certain higher odd and even levels. Use was then made of the Ritz combination principle to calculate precise wavelength values of approximately sixty copper lines in the region between 1663 A and 984 A with estimated accuracies which varied from ±0.0003 A to ±0.001 A.

Contribution to the First Spark Spectrum of Germanium (Ge ii)

Observations of the spark spectrum of Ge from 4741 A to 7145 A have made possible the improvement of certain of the term values of Ge ii. By combining their interferometric wavelength measurements with unpublished data of C. W. Gartlein the authors were able to determine the fine structure of four 4s2nf2F° terms of Ge ii. All the terms for n = 4, 5, 6, and 7 are inverted and the splittings range from 0.47 to 0.75 cm−1. Values were obtained for the unresolved 4s2ng2G terms for n = 6 and 7.

Tertiary Interferometric Wavelength Standards from Measurements on Lines of the 2-0 Band of Carbon Monoxide and Derived Wavelength Standards for Some Lines of the 1-0 Band of Carbon Monoxide The Velocity of Light Derived from a Band Spectrum Method IV*

Interferometric wavelength measurements have been made on thirty-three lines of the 2–0 band of CO at 4260 cm−1. These measurements were made relative to R(18) of this band, which had previously been measured against the Hg198 green line, and have a relative accuracy of 1 part in 107. The R(6) line of the 3–0 band has also been measured interferometrically. These data, when combined with results of other investigators, give the following values for constants, all in cm−1:B0=1.922521±0.0000035D0=6.117×10−6±0.01×10−6B2−B0=−0.035008D2−D0=−1.9×10−9Be=1.931285αe=0.017535γe=1.01×10−5βe=−1.0×10−9ωe=2169.829xeωe=13.295yeωe=0.0115.The precise constants allow wavelengths to be calculated for the 1–0 band at 2143 cm−1. Since accurate measurements in this region are difficult to make, it is felt that these calculated values are more accurate than any measured values so far reported.The value of B0, when combined with recent microwave results, gives for the velocity of light c=299 793.7±0.7 km/sec.

Interferometric Wavelength Measurements of Germanium Lines of a Hollow Cathode Discharge*

Interferometric wavelength measurements of forty-three germanium arc lines in the region from 4685 A to 2019 A have been performed. The light source used was a hollow cathode Schüler tube of special design employing a cast germanium cathode provided with a slot. The precision measurements carried out by means of a Fabry-Perot interferometer equipped with 6, 20, 36, and 49 mm spacers show that the germanium lines emitted by this source are of superior quality and merit use as secondary standards.The measurements were employed for the establishment of precision values for one even energy level and for eighteen odd levels. Furthermore, by application of Ritz’s combination principle and by using the term analysis of the spectrum it was possible to calculate precisely the wavelength values of twenty-nine germanium lines in the vacuum region between λ1998 A and λ1691 A. These lines can be recommended as reliable standards in this wavelength region.

Interferometric Wavelengths of Iron Lines from a Hollow Cathode Discharge*

Interferometric wavelength measurements (3570 A to 5709 A) are given for 189 iron lines produced by a hollow cathode discharge. The lines are considerably sharper than those of the iron arc and the available evidence shows that the wavelengths are invariant with any changes in operating conditions of the tube. The hollow cathode discharge tube in neon with iron electrodes appears to be the best source of standards for wavelength measurements.

A Simulated Channel Spectrum*

In order to obtain the highest accuracy in interferometric wavelength measurements with energy integrating devices, the theory of the Fabry-Perot interferometer must be extended. In this paper the portion of the theory dealing with the integrated energy in the part of the Fabry-Perot ring system virtually intercepted by a slit of finite length is presented. We are assuming that the interferometer is placed in parallel light and an infinitely narrow band of wavelengths is used. For this situation, it is shown how the order at the center of the ring pattern corresponding to maximum and minimum energies respectively varies with slit height. The contrast is then determined as a function of slit height. The experimental methods for measuring these quantities are described and the results compared with theory. The theory is also extended to the case of an actual channel spectrum where a finite band of wavelengths is present.

Interferometric Wavelength Measurements in the Near Infrared*

Interferometric Wavelength Measurements in the Near Infrared*

Structure of theD2Terms of the Arc Spectrum of Lithium

Interferometric wave-length measurements of high precision carried out by employing an atomic beam light source have been used for the study of several features of the arc spectrum of ${\mathrm{Li}}^{7}$. Due to the great sharpness of the spectral lines produced by this source it was possible to determine the splitting of several $^{2}D$ terms. The hyperfine structure of the line 6708A was found in approximate agreement with earlier investigations. Precise wave-length measurements have been carried out relative to krypton standards. Discrepancies between the wave-lengths of this investigation and those of earlier investigators must be ascribed to lack of resolution or inadequate comparison methods employed in earlier investigations. This consideration is substantiated by our measurements carried out with a vacuum lithium arc, the results of which are consistent with the atomic beam values. Isotopic shift (${\mathrm{Li}}^{6}$ and ${\mathrm{Li}}^{7}$) of the resonance line 6708A was measured.