Angular momentum coupling atoms

IV. Angular Momentum Coupling and Atoms in Crossed Fields... 

IV. ANGULAR MOMENTUM COUPLING AND ATOMS IN CROSSED FIELDS... 

Angular momentum coupling is just a mathematical device, which does not explain why the two states actually have different energies. The theory does, however, make some useful predictions. When an atom with spin-orbit coupling is subjected to a magnetic field, it is the total angular momentum that can take a variety of orientations, and the number allowed is given the formula (2j + 1), in line with the similar formulae for s and l. For example, the levels j = f and i split into four and two states, respectively, which can... 

There are two extreme approaches to the description of vibroiiic states in crystals. The crystal states may be regarded as products of molecular vibronic states, or as linear combinations of vibronic site states. In the former case the electrons and nuclei in the unit cell couple independently, while for the latter description the intramolecular vibronic interactions are assumed to dominate. These two approaches are somewhat analogous to y and LS coupling of spin and orbital angular momentum in atoms and are called strong and weak coupling, respectively. The approach to the classification of states is different for each case. 

The book by Johnson covers nonrelativistic and relativistic atomic structure theory, providing many details on angular momentum coupling as well as a bridge to numerical solution methods. 

Complexes formed from atoms and linear polyatomic molecules are very similar to atom-diatom systems the coupled equations are identical, and the same angular momentum coupling schemes apply. The only added degree of complexity is that perpendicular transitions of the polyatomic monomer are possible, and these introduce an extra quantum number (/ or k) for the monomer vibrational angular momentum. Such states are analogous to those arising from A > 0 states of a symmetric top monomer, as discussed below. 

ANGULAR MOMENTUM COUPLING IN MANY-ELECTRON ATOMS... 

The multiplet structure in Ne arises from a pair-coupling (not Russell-Saunders) angular momentum coupling scheme, which is obeyed in rare-gas atom excited states. The ground and excited states of Ne exhibit the electron... 

Discuss the two angular momentum coupling schemes, LS and jj coupling. How can it be determined experimentally which coupling scheme is relevant for a particular atomic configuration ... 

More generally, further complications arise for angular momentum couplings when the fragments show electronic angular momentum, but the fundamental symmetry rules are not affected by this. Early examples for detailed correlations include triatomic systems, and another more recent example is the correlation for atom + linear molecule. While for such simple cases, and planar molecules in general, parity is... 

Transitions from one electronic state of an atom to another electronic state can be induced by electromagnetic radiation. The spectra of many-electron atoms tend to be complicated because there are numerous electron occupancies and states. As well, each of the many electrons is a source of angular momentum and magnetic dipoles that interact. Angular momentum coupling rules can help sort through the manifolds of atomic electronic states. 

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