Atoms alkali, hyperfine structure

For each of the alkali metals used the e.s.r. spectrum at 77°K consisted of a single narrow line (Fig. 12a, b). The relevant features of the e.s.r. spectra are summarized in Table 4. The absence of any effect of the cation on the line width or p-factors shows conclusively that the electron has been transferred completely from the alkali metal atom and is therefore not held in an expanded orbital around the cation, as suggested by Jortner and Sharf (1962). The difference in line width between the spectra in D2O (3-2 G) and in water (9-2 G) suggests that there is a hyperline interaction between the electron and the protons in water. This was shown conclusively by the observation of seven equally spaced hyperfine lines when a deposit prepared from water was warmed carefully (Fig. 12c), whereas no hyperfine structure was observed from a sample containing deuterium oxide. The hyperfine structure shows that the electron interacts primarily with six protons and that it is not delocalized over a large number of water molecules but is located in a well-defined trap surrounded by these protons. 

In most studies of this section the influence of the polarization of the emission has been neglected. If polarization is present, the anisotropy in the emission must be taken into account when calculating an emission cross section.1 However, it has been shown21 that due to the hyperfine structure of the alkali atoms the polarization of the sodium and potassium resonance lines is less than 20 %. In these cases the influence of the polarization on the angular distribution of the emitted photons can be neglected. 

Like solvated electrons, the pairs and the atoms are paramagnetic. Their ESR spectra reveal hyperfine structure arising from the interaction of the electron s spin with the spin of alkali nucleus. The coupling constant increases enormously with rising temperature, an increase unmatched by those observed in any other systems. This observation is consistent with the proposed dynamic equilibrium between the pairs and the atoms, higher temperatures favor the unionized atom. Apparently, the rate of conversion is high... 

Trapped electrons are furthermore formed by the deposition of alkali-metal atoms on pure ice at 77°K. (3). The ice samples were microcrystalline or amorphous and from the ESR spectrum which exhibited hyperfine structure one could draw the conclusion that the electron was located in a well defined trap in which it was surrounded by six protons. The optical absorption band had a broad plateau ranging from about 600 to 680 n.m. 

Zeeman Eefectinthe Hyperfine Structure of Alkali-Metae Atoms... 

In Chap. 7 we have discussed how hyperfine structure can be determined by level-crossing spectroscopy. Clearly, alkali atom states can readily be studied using this technique after step-wise excitation. We will here instead choose an example illustrating fine-structure measurements. In Fig.9.17 the example of the inverted sodium 4d 05/2,3/2 given. 

S. Svanberg, P. Tsekeris, W. Happen Hyperfine structure studies of highly excited D and F levels in alkali atoms using a CW dye laser. Phys. Rev. Lett. 30, 817 (1973)... 

If the nucleus has no spin, i.e. I — 0, there is neither a magnetic nor an electric hyperfine structure. For I — lj2 only a magnetic interaction is possible, whereas the occurrence of electrical hyperfine structure requhes I > 1 and J > 1. Hyperfine stmctiue and the determination of nuclear moments have been discussed in [2.47]. Extensive data on nuclear moments have been listed in [2.48, 2.49] hfe data for the extensively studied alkali atoms have been compiled in [2.50] and the theoretical aspects of atomic hyperfine interactions have been covered in [2.51-2.54]. 

Measurements at high fields, gjUp B > Aj. Hyperfine structure separations, " j pg can also be obtained from measurements of the frequencies of the AMj= 1, AMj=0 transitions induced when the C-field is sufficiently strong that and J are completely decoupled. For an alkali atom equation (18.19) shows that these transitions occur at frequencies given by... 

Magnetic tuning of diatomic bound-state and scattering properties relies on the Zee-man effect in the hyperline structure of alkali-metal atoms. The splitting into sublevels of the 5i/2 electronic ground state of such an atom which is exposed to a magnetic field B can be described by the following Hamiltonian comprised of hyperfine and Zeeman interactions [27] ... 

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