Magnetic field Zeeman effect

In 1925, Wolfgang Pauli gave chemists what they wanted from the physicists a physical principle underlying electron-pair valency. Pauli built on the fact that in addition to the continuous, line, and band spectra, there is a fine structure of doublets, triplets, and multiple lines, some of which are split in a magnetic field (Zeeman effect). 

Figure 9.6 Molecular hydrogen and NMR spectroscopy, (a) Energy levels of an A2 spin system depending on the strength of the magnetic field (Zeeman effect), (b) NMR transitions and resulting NMR spectrum (shown schematically).

The notion of electronic spin was first proposed by Uhlenbeck and Goudsmit in 1925 to account for the sphtting of some of the lines seen in atomic spectra. They and others showed that the electronic spin also accounted for the anomalous effects of magnetic fields (Zeeman effects) on the spectra of many atoms. However, it was necessary to postulate that the magnetic moment associated with electronic spin is not simply the product of the angular momentum and ejlmc, as is true of orbital magnetic moments, but rather twice this value. The extra factor of 2 is called the Lande g factor. When Dirac [33] reformulated quantum mechanics to be consistent... 

In summary, the Hamiltonian of an atom exposed to a magnetic field (Zeeman effect) can be broken down into the following components the core Hamiltonian, the electron-electron repulsion, the spin-... 

The interaction of the spin magnetic moment with the orbital magnetic moment of the unpaired electron leads to an orientationally dependent shift of the resonance frequency. This effect is normally described by an effective spin operator S and an anisotropic g matrix. The quantimi-mechanical Hamilton operator for the interaction of the electron spin with the external magnetic field Zeeman interaction) can, therefore, be described by... 

Zeeman effect The splitting of atomic spectral lines by a magnetic field. This effect was found by the Dutch physicist Pieter Zeeman (1865-1943) in 1896. Some of the patterns of line splitting that be explained both by classical electron theory and the BOHR THEORY of electrons in atoms. The Zeeman splitting that can be explained in these ways is known as the normal Zeeman effect. There exist more complicated Zeeman splitting patterns that cannot be explained either by classical electron theory or the Bohr theory. This more complicated type of Zeeman effect is known as the anomalous Zeeman effect. It was subsequently realized that the anomalous Zeeman effect occurs because of electron spin and that the normal Zeeman effect occurs only for transitions between singlet states. 

We stress the fact that in this chapter we are concerned only with the low field Zeeman effect of the even isotopes of an element. This simplification is not fundamental and is made purely for the sake of clarity of exposition. The effects of hyperfine structure in the odd isotopes and of the decoupling of the electronic and nuclear spins which occurs in large magnetic fields will be considered in Chapter 18. 

Not only can electronic wavefiinctions tell us about the average values of all the physical properties for any particular state (i.e. above), but they also allow us to tell us how a specific perturbation (e.g. an electric field in the Stark effect, a magnetic field in the Zeeman effect and light s electromagnetic fields in spectroscopy) can alter the specific state of interest. For example, the perturbation arising from the electric field of a photon interacting with the electrons in a molecule is given within die so-called electric dipole approximation [12] by ... 

In practice, the emission line is split into three peaks by the magnetic field. The polariser is then used to isolate the central line which measures the absorption Ax, which also includes absorption of radiation by the analyte. The polariser is then rotated and the absorption of the background Aa is measured. The analyte absorption is given by An — Aa. A detailed discussion of the application of the Zeeman effect in atomic absorption is given in Ref. 51. 

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