Second-Doppler effect

The quadrupole shift is eliminated by averaging the frequency measurements on three orthogonal orientations, resulting in a fractional uncertainty of 0.5 x 10 I Estimation of all of the systematic effects (electric fields, gravity, second-Doppler effect, etc.) have yielded a correction of 1.727 Hz, with a total fractional uncertainty of 7.2 X 10" . The absolute frequency of the transition was measured with a frequency comb vs cesium to be 1064,721,609,899,144.94 Hz, with a statistically limited total fractional uncertainty of 9.1 x 10 , which is the most accurate absolute measurement of an optical frequency to date. 

The second factor involves the theory that defines the natural width of the lines. Radiations emitted by atoms are not totally monochromatic. With plasmas in particular, where the collision frequency is high (this greatly reduces the lifetime of the excited states), Heisenberg s uncertainty principle is fully operational (see Fig. 15.4). Moreover, elevated temperatures increase the speed of the atoms, enlarging line widths by the Doppler effect. The natural width of spectral lines at 6000 K is in the order of several picometres. 

Figure 3.5 Doppler effect with calcium source, indicated by 4. The calcium line in the spectrum at top is redshifted in the bottom spectrum because the source is moving away from Mr. Plex. For stars moving tens of thousands of miles per second away from us, the redshift can be quite pronounced.

Fig. 10. Extrapolation of the half maximum center (o) and of the line position corrected for the light-shift, second order Doppler effect and 8D hyperfine structure ( ) versus the light power P in the case of the 2 >i/2 (F = 1) — 8D5/0 transition of deuterium...

Abstract. This paper deals with high resolution spectroscopy of hydrogen and deuterium atoms. The 1S-3S and 2S-6S/D transitions have been used to determine the ground state Lamb shift with an accuracy of 46 kHz. The aim of the present experiment is to make an absolute frequency measurement of the 1S-3S transition. We present in this paper the improvement on the experiment and the developpment of a new method to compensate the second order Doppler effect by the application of a magnetic field. 

Secondly, in the atomic frame, it comes with a motional electric field E = V x B hydrogen atom are specially sensitive to this field. As this electric field is proportional to v, the corresponding shift of the S level due to the interaction with a near P level, is quadratic with v. Moreover, since the nearest level (P1/2) is below the S one, this motional electric field can give a positive frequency shift of the transition Av able to compensate the negative shift due to the second order Doppler effect. 

We have improved the signal to noise ratio of the experiment by a factor 15, this allows us to determine very precisely the 1S-3S transition frequency with a reasonnable integration time. The preliminary results for the second order Doppler effect are very stimulating. We plan to make more precise measurements of this effect. The frequency chain to make an absolute frequency measurement is in preparation in the Laboratoire Primaire du Temps et des Frequences. The determination of the absolute frequency of the 1S-3S transition is planed within one year. 

In both atomic hydrogen and deuterium we have studied the three transitions 2S - 8Da/z, 2S1/s- 10D3/z and 2S1/g- 12D3/2. The frequencies measured, corrected for hyperfine splittings and for the second-order Doppler effect, are reported in Table I. 

Besides the IS there exists a shift of the Mossbauer lines due to the second-order Doppler effect (i3, 14). This shift is given by... 

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