Electronic structure Zeeman effect

When a spectral line source is subject to a magnetic field, the spectral lines display hyperfine structure (Zeeman effect). In order to explain hyperfine structure it is postulated that the electron rotates on its axis with spin angular momentum S ... 

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). 

From accurate measurements of the Stark effect, when electrostatic fields are applied, information about the electron distribution is also obtained. Further information is obtained from nuclear quadrupole coupling effects and Zeeman effects <1974PMH(6)53>. Microwave studies also provide important information regarding molecular force fields, particularly with reference to low-frequency vibrational modes in cyclic structures <1974PMH(6)53>. 

In 1926 it was realized that there is a property of the electron other than the charge which must be taken into account, namely, the magnetic moment associated with intrinsic spin. It was shown by Goudsmit and Uhlenbeck [53] that this property, which represents an extra degree of freedom and therefore demands a fourth quantum number, could account for the doublet structure of the alkali spectra and the anomalous Zeeman effect. If was necessary and sufficient that the extra quantum number he two-valued. 

Radford (1961, 1962) and Radford and Broida (1962) presented a complete theory of the Zeeman effect for diatomic molecules that included perturbation effects. This led to a series of detailed investigations of the CN B2E+ (v — 0) A2II (v = 10) perturbation in which many of the techniques of modern high-resolution molecular spectroscopy and analysis were first demonstrated anticrossing spectroscopy (Radford and Broida, 1962, 1963), microwave optical double resonance (Evenson, et at, 1964), excited-state hyperfine structure with perturbations (Radford, 1964), effect of perturbations on radiative lifetimes and on inter-electronic-state collisional energy transfer (Radford and Broida, 1963). A similarly complete treatment of the effect of a magnetic field on the CO a,3E+ A1 perturbation complex is reported by Sykora and Vidal (1998). The AS = 0 selection rule for the Zeeman Hamiltonian leads to important differences between the CN B2E+ A2II and CO a/3E+ A1 perturbation plus Zeeman examples, primarily in the absence in the latter case of interference effects between the Zeeman and intramolecular perturbation terms. 

Subjects of recent publications on the spectroscopic properties and electronic structure of porphyrins include the photochemically induced dichroism of [(aetio)Zn]-,380 the absorption spectra of metallo-TPP compounds in SF , Ar, and n-octane matrices,361 the Zeeman effect in the absorption spectra of Pd-porphin in n-octane single crystals,362 the electronic spectra of Cu11- and Niu-corrin derivatives,363 m.c.d. studies on porphyrins,864 866 photoelectron spectra of porphyrins and pyrroles,366 and quantum mechanical calculations on porphyrins.367 368... 

AI and Cq (see Chapter 2.14 for further details) are related to molecular electronic structure by Equations (2) and (3), where /) is the excited state of the corresponding MCD transition, df is the electronic degeneracy of the ground state A) and the summation is over all components of 1 4) and /). The first part of the /4-term expression is the difference between the excited and ground-state eman terms, while the first part of the C-term expression gives the Zeeman effect in the ground state. The second parts in both equations give the difference between the Icp (m+) and rep (m ) electric dipole moments ... 

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