Hyperfine structures, atomic spectroscopy

Dey] Mossbauer spectroscopy Magnetic hyperfine structure, atomic magnetic ordering... 

Moseley s law spect The law that the square-root of the frequency of an x-ray spectral line belonging to a particular series is proportional to the difference between the atomic number and a constant which depends only on the series. mOz-lez, 10 Mossbauer spectroscopy spect The study of Mossbauer spectra, for example, for nuclear hyperfine structure, chemical shifts, and chemical analysis. mus,bau-3r spek tras ko pe ... 

The reversible formation of a low-spin [Co (III) (NHS) n02 ]2+ complex within a Co (II) Y zeolite has been demonstrated by EPR spectroscopy. In this complex n is probably equal to five. A maximum of one cobalt complex per large cavity was farmed. The cobalt hyperfine structure shows that the unpaired electron is only 8% on the metal ion. Experiments utilizing 170 indicate that 02 enters the coordination sphere of the Co2+ ions and that the unpaired electron is largely associated with the oxygen molecule. The oxygen-17 hyperfine structure reveals that the two oxygen atoms are not equivalent hence, it is concluded that the oxygen is bonded as a peroxy-type superoxide ion. 

Hyperfine structure measurements using on-line atomic-beam techniques are of great importance in the systematic study of spins and moments of nuclei far from beta-stability. We will discuss the atomic-beam magnetic resonance (ABMR) method, and laser spectroscopy methods based on crossed-beam geometry with a collimated thermal atomic-beam and collinear geometry with a fast atomic-beam. Selected results from the extensive measurements at the ISOLDE facility at CERN will be presented. 

Prior to about 1955 much of the nuclear information was obtained from application of atomic physics. The nuclear spin, nuclear magnetic and electric moments and changes in mean-squared charge radii are derived from measurement of the atomic hyperfine structure (hfs) and Isotope Shift (IS) and are obtained in a nuclear model independent way. With the development of the tunable dye laser and its use with the online isotope separator this field has been rejuvenated. The scheme of collinear laser/fast-beam spectroscopy [KAU76] promised to be useful for a wide variety of elements, thus UNISOR began in 1980 to develop this type of facility. The present paper describes some of the first results from the UNISOR laser facility. 

The second phase will be designed and constructed based on the results of Phase 1. While the focus is on 2-photon laser spectroscopy of magnetically trapped antihydrogen atoms, other measurements (e.g. a measurement of the hyperfine structure using an atomic antihydrogen beam) are being explored for this program. 

Relativistic effects play an important role in the spectroscopy of atoms and molecules whenever heavy atoms are involved or electronic or nuclear spins become significant, as in ESR and NMR spectroscopy or for the fine and hyperfine structure of electronic states. Also the chemical behaviour of the heavy elements, beyond Z 50, is strongly influenced by relativistic effects. As the chemical interactions are affected by the slow valence electrons, relativistic effects were thought to be of minor importance. However, electrons of shells with low / values, especially s electrons, do penetrate the atomic core and experience relativistic retardation effects near highly charged nuclei these shells therefore contract. On the other hand, electrons in shells with higher / values, / 2, are screened better, due to the contracted s shells, from the nuclear charge and therefore become destabilized thus these shells are more expanded than expected. 

Childs, W. J. and Goodman, L. S., "Hyperfine structure and isotope-shift measurements on Dy I 5988.562 using high-resolution laser spectroscopy and an atomic beam,"... 

Thermal atomic beams have been used extensively to determine nuclear spins and moments by investigations of the atomic hyperfine structure. The atomic-beam magnetic resonance (ABMR) method has already become classical [2]. More recent efforts include laser spectroscopy in a crossed-beam geometry, in which a large supression of the Doppler width is obtained by collimation of the atomic beam. 

Millimeter wave spectroscopy with a free space cell such as a Broida oven is more sensitive than lower frequency microwave spectroscopy. However, the higher J transitions monitored by millimeter wave spectroscopy often do not show the effects of hyperfine structure. In the case of CaOH and SrOH, the proton hyperfine structure was measured in beautiful pump-probe microwave optical double resonance experiments in the Steimle group [24,68], They adapted the classic atomic beam magnetic resonance experiments to work with a pulsed laser vaporization source and replaced the microwave fields in the A and C regions by optical fields (Fig. 15). These sensitive, high-precision measurements yielded a very small value for the proton Fermi contact parameter (bF), consistent with ionic bonding and a... 

The structure, spectroscopy and chemistry of heavy atoms exhibit large relativistic effects. These effects play an important role in lighter elements too, showing up in phenomena such as fine or hyperfine structure of electronic states. Perturbative approaches, starting from a non-relativistic Hamiltonian, are often adequate for describing the influence of relativity on light atoms for heavier elements, the Schrodinger equation must be supplanted by an appropriate relativistic wave equation. 

Doppler-free two-photon transitions to atomic Rydberg levels [251] allow the accurate determination of quantum defects and of level shifts in external fields. Hyperfine structures in Rydberg states of two-electron atoms, such as calcium and singlet-triplet mixing of the valence state 45 and and Rydberg levels have been thoroughly studied by Doppler-free two-photon spectroscopy [252]. 

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