Absolute wavelength measurements

Freiburg [22] and an electron-cyclotron-resonance ion trap (ECRIT) [23], it may soon be possible to make absolute wavelength measurements of the Lyman-a transitions in hydrogen-like ions, using hat or double hat crystal spectrometers. 

Carlsson G, Kastberg A and Pendrill L R 1996 Absolute wavelength measurement of Cs D2 resonance line , submitted for publication... 

The MI can be used for absolute wavelength measurements by counting the number N of maxima in B when the mirror M2 is moved along a known... 

Resolving power and light-gathering power are not the only criteria by which a wavelength-dispersing instrument should be judged. A very important question is the attainable precision and accuracy of absolute wavelength measurements. 

For absolute wavelength measurements of spectral lines the laser is stabilized onto the center of the line and its wavelength X is measured with one of the wavemeters described in Sect. 4.4. For Doppler-free lines (Chaps. 7-11), one may reach absolute wavelength determinations with an uncertainty of smaller than 10 cm" (= 20pm at A, = 500 (xm). 

Fig. 5.58. (a) Schematic diagram of computer-controlled laser spectrometer with frequency marks provided by two FPI with slightly different free spectral ranges and a lambdameter for absolute wavelength measurement, (b) Scheme for wavelength determination according to (5.93c)... 

An absolute wavelength measurement on the same transitions 2 2 Pj was performed by Holt et to improve the experimental value of... 

With the ultrahigh resolution, which can, in principle, be achieved with singlemode tunable lasers (Vol. 2, Chaps. 1-5), the accuracy of absolute wavelength measurements attainable with conventional techniques may not be satisfactory. New methods have been developed that are mainly based on interferometric measurements of laser wavelengths. For applications in molecular spectroscopy, the laser can be stabilized on the center of a molecular transition. Measuring the wavelength of such a stabihzed laser yields simultaneously the wavelength of the molecular... 

The widely used plane Fabry-Perot interferometer (F.P.I.) is applied to absolute wavelength measurements and high-resolution studies of spectral line profiles. Since its spectral resolving power may exceed 10, spectral profiles of Doppler-broadened or pressure-broadened lines can be studied with this instrument. 

In most of the methods discussed so far in high-resolution laser spectroscopy, the laser frequency was tuned across the molecular absorption spectrum and the frequency separation of different lines was determined either by interpolation between frequency marks provided from a long F.P.I., or by absolute wavelength measurements, using one of the methods explained in Sect.4.4. For many problems in spectroscopy, however, it is important to know accurately the splittings of closely separated lines rather than their absolute wavelengths. Examples are the hfs, Zeeman, or Stark splittings. 

Fig. 3. Experimental arrangement for polarization spectroscopy with absolute wavelength measurements with a travelling Michel son wavemeter.

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