Separated oscillatory fields

N. F. Ramsey (Harvard) invention of the separated oscillatory fields method and its use in the hydrogen maser and other atomic clocks. 

Separated Oscillatory Field Measurement of the Lamb Shift in H, n=2 ... 

This paper reports a precision measurement of the Lamb shift in the n=2 state of hydrogen using separated oscillatory fields in conjunction with a fast atomic beam. Atoms in the 2 S 2 metastable state are produced through charge capture by protons in a gas target. The atoms pass thrugh two separated oscillatory fields whose relative phase is switched between 0 and ir. A rf quenching field and a solar blind... 

The fast beam separated oscillatory field technique (SOF) provides a method through which one can obtain a series of lines whose widths are less than the natural line width with a good understanding of the factors which determine the line shape and the line center. This paper summarizes a separated oscillatory field measurement of the Lamb shift in hydrogen.[1]... 

To select one hyperfine state the preparation quench plates are driven at 1110 MHz and the detection quenching plates are driven at 910 MHz. Figure 3 shows the microwave system used to produce the two separated oscillatory fields. A high precision coaxial magic Tee drives the two rf regions so that they have relative phases of 0° or 180°. Figure 4 shows the hyperfine state selection. 

Figure 5 shows the average quench and interference signals obtained with a 100 keV beam and increasing separation of the rf regions. The envelope of the interference signal is determined by the spatial distribution of the rf field in the two separated oscillatory field regions. 

Fig. 3 The system used to power the separated oscillatory fields...

The fast beam separated oscillatory field method has been used to measure with high precision the Lamb shift in the n=2 state of hydrogen. The agreement between the measured value and the theoretical value is obscured by the discrepant values for... 

The drive for accuracy produced Ramsey s separated oscillatory field method however, there were limits to how far apart the two... 

Atomic Hyperfine Structure, Separated Oscillatory Fields and... 

ATOMIC HYPERFINE STRUCTURE, SEPARATED OSCILLATORY FIELDS AND ATOMIC CLOCKS... 

Ramsey, N.H. Experiments with separated oscillatory fields and hydrogen masers. Rev. Mod. Phys. 1990, 62, 541-554. 

To overcome this problem Ramsey (1949) introduced the method of two separate oscillatory field loops, through which the atomic beam passes at the beginning and end of the C-field. It is then only necessary for the average value of the C-field between the loops to be equal to the field at each of the loops, and its magnitude can be determined by proton NMR. An interference pattern is observed with resonances narrower by some 40% than with a single oscillatory field over the same length. [A classical analogy is with Michelson s two-slit stellar interferometer.]... 

Experimental methods of measuring the Lamb shift can be broadly classified into two basic types. The first is the microwave resonance technique originally used by Lamb and Retherford, in which the 2s - 2p transition is observed directly in a microwave cavity. The prime factor limiting the accuracy is the precision with which the resonance line center can be located. Since the width r of the 2pi state is about one tenth of the Lamb shift, the line center must-be located to a precision of lOx ppm relative to F for a precision of x ppm n the Lamb shift. Line narrowing can be achieved by use of Ramsey s separated oscillatory fields technique, but at the expense of a lower signaj-to-noise ratio. Since the Lamb shift increases in proportion to Z, the f quency lies outside the micro-wave region for ions heavier than Li. A tunable laser can then be used in conjunction ith a fast ion beam as further discussed below. 

Three recent measurements shown in Table 1 and Fig.4 provide particularly significant tests of theory. The first is the high precis gn (+9 ppm) microwave resonance measurement of Lundeen and Pipkin, using the separated oscillatory field method. Their result lies well below both theoretical values when the Borie correction is excluded, but agrees with Mohr s theory when the Borie correction is included. The influence of the Borie correction is particularly large in the case of deuterium, but here the experimental data are insufficiently precise to provide a definitive test. A measurement in deuterium similar in precision to Lundeen and Pipkin s result in hydrogen would provide a valuable check on the validity of the Borie correction. 

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