Hyperfine transitions

Similarly, the hyperfine transitions involving the spin-mixed Zeeman states within the Is level are expected to display frequency shifts due to CPT violation. In particular, the transition from the low field seeking Is — c states to the Is — d states could provide an unsupressed evidence of CPT violation that leads to differences between H and H A,h-h, -H fi... 

Precise measurements on g factors of electrons bound in atomic Hydrogen and the Helium ion 4He+ were carried out by Robinson and coworkers. The accuracies of 3 x 10-8 for the Hydrogen atom [5] and of 6 x 10-7 for the Helium ion [6] were sensitive to relativistic effects. Other measurements of the magnetic moment of the electron in Hydrogen-like ions were performed at GSI by Seelig et al. for Lead (207Pb81+) [7] and by Winter et al. for Bismuth (209Bi82+) [8] with precisions of about 10-3 via lifetime measurements of hyperfine transitions. These measurements were also only sensitive to the relativistic contributions. 

Abstract. We present a review of the helium spectroscopy, related to transitions between 23S and 23P states around 1083 nm. A detailed description of our measurements, that have produced the most accurate value of the 23Po — 23Pi fine structure interval, is given. It could produce an accurate determination (34 ppb) of the fine structure constant a. Improvements in the experimental set up are presented. In particular, a new frequency reference of the laser system has been developed by frequency lock of a 1083 nm diode laser to iodine hyperfine transitions around its double of frequency. The laser frequency stability, at 1 s timescale, has been improved of, at least, two orders of magnitude, and even better for longer time scales. Simultaneous 3He —4 He spectroscopy, as well as absolute frequency measurements of 1083 nm helium transitions can be allowed by using the Li-locked laser as frequency standard. We discuss the implication of these measurements for a new determination of the isotope and 23 5 Lamb shifts. 

The lack of accurate and stable frequency standards in the near-infrared spectral range, and in particular at 1083 nm, is a serious inconvenient to improve the present frequency stability of the He-locked master laser. On the other hand, hyperfine transitions of the iodine molecule has been defined as secondary frequency standard at different visible wavelengths, and in particular at 532 nm, the doubled frequency of the 1064 nm Nd YAG laser. Likewise, our idea has been to lock the master laser frequency to I2 hyperfine transitions at its doubled frequency, 541 nm. 

NMR frequency of 7Li was measured relative to the hyperfine transition in the ground state of hydrogen to search for a diurnal variation of the ratio of these... 

Note that this value and its uncertainty is valid only for this particular iodine cell (16/89PTB) and must not be confused with the value and uncertainty of the unperturbed value of this hyperfine transition. The frequencies of iodine cells from different origins may scatter more than the uncertainty of the absolute frequency measurement reported here. However, cell 16/89PTB has participated in an international comparison of iodine cells at BIPM and found to have a frequency shift of Z zz16/89 = + 2.6 (2.8) kHz with respect to an iodine cell used as reference in the BIPM4 He-Ne frequency standard [26]. 

We come now to the second study, described ten years later [23]. The main development was the employment of a tunable dye laser to pump the A <— X + transition. Rotational levels in the ground state with J = 1 to 29, in the v = 0 vibrational level, were pumped by the laser and radioffequency hyperfine transitions studied. The range of J levels studied meant that the effective Hamiltonian required the addition of terms describing the dipolar and scalar interactions between the 23Na nuclear spins. These terms were given earlier in our discussion of the D2 molecule, and the complete effective Hamiltonian is ... 

The lowest level studied experimentally was. 7=1, for which seven hyperfine transitions were observed and the molecular constants determined [23]. For an odd J value the allowed values of / are 1 and 3, so that the following hyperfine levels exist ... 

Figure 8.24. Section of the radio frequency spectrum of N2 in its A state. The observed resonances involve two different hyperfine transitions in two different rotational levels, and arise from eight different vibrational levels, v = 0 to 7, as shown. The transitions are all AMF = 0 and were recorded at a magnetic field of 150 mG [44].

Substituting these values in (8.276) we obtain the following values for the hyperfine energies, and the frequency of the hyperfine transition (all in MHz) ... 

Table 8.24. A-doublet hyperfine transition frequencies recorded for the OH radical...

OH is the only coma constituent which has been found in the ultraviolet, in the optical and in the microwave region. Its two hyperfine transitions at 18 cm (1665 and 1667 MHz) have been identified in 7 recent comets, among them the two periodic comets d Arrest and Encke. Generally, the line intensities were in agreement with the assumption of ultraviolet pumping by the solar radiation. This model did, however, not fit to the observations of the two periodic comets. Possibly, this is a... 

This cosmic spectroscopy method has been extended to study variation of other fundamental parameters. The ratio of the hydrogen atom hyperfine transition frequency to a molecular (CO, CN, CS, HCO" ", HCN etc.) rotational frequency is proportional to y = a gp where Qp is the proton magnetic gr-factor [21]. A new prehminary result here is Ay/y = (—2.4 1.8) X 10 about 4 billion light years from us (the average z=0.47). Altogether, we now have 3 independent samples of data two optical samples (see [2,3]) and one radio sample. All 3 samples hint that Aa is negative. 

---