In most quantum mechanics textbooks,the determination of coupling vectors of multiple angular momentums was usually by looking up tables because of its complex calculation.It was introduced another method for the determination of coupling vectors,with the coupling of orbit-spin angular momentum of electrons as an example.
The vector model is examined in the light of the quantum theory of wave fields. First the distributions of electrons among the electronic states are limited to correspond to the atomic states arising from one electronic configuration. A set of independent angular momentum vectors 11, 12,...S1, S2... is found, in which one orbital and one spin vector are associated with each group of electronic states, rather than individual electrons, having given values of the quantum numbers n and l. Any other vector T may be decomposed into a sum of independent vectors ti, one associated with each of the same group of electronic states. The usual commutation relations obtain among the vectors ti, li and si. On further limiting the distributions to correspond to atomic states arising from electronic configurations containing no equivalent electrons, it is shown that the matrix of ${\ensuremath{\Sigma}}_{k}f({{\mathrm{l}}_{k}}^{0}, {{\mathrm{s}}_{k}}^{0})$ (an operator in coordinate space in which f is any algebraic function of the components of 1 and s) can be constructed from the vectors 11, 12...S1, S2,... according to the usual laws of matrix mechanics.
This book offers a concise introduction to the angular momentum, one of the most fundamental quantities in all of quantum mechanics. Beginning with the quantization of angular momentum, spin angular momentum, and the orbital angular momentum, the author goes on to discuss the Clebsch-Gordan coefficients for a two-component system. After developing the necessary mathematics, specifically spherical tensors and tensor operators, the author then investigates the 3- j , 6- j , and 9- j symbols. Throughout, the author provides practical applications to atomic, molecular, and nuclear physics. These include partial-wave expansions, the emission and absorption of particles, the proton and electron quadrupole moment, matrix element calculation in practice, and the properties of the symmetrical top molecule.
The theory of angular momentum performance a significant position in the classical and quantum mechanical study of physical properties, such as studies into nuclear, atomic, and molecular processes, as well as other quantum problems, including spherical symmetry. In this analysis, angular momentum operators are described in multiple ways, based on the angular momentum operator's commutator, matrix, and geometric representation, The eigenvalue and eigenvector were also known for operatorsJ ̂_±,J ⃑ ̂^2, J ̂_x,J ̂_y and J ̂_zwithin the |j,┤ ├ m⟩ basis. Furthermore, in quantum mechanics, angular momentum is called quantized variable, meaning that it comes in discrete quantities. In contrast to the macroscopic system case where a continuous variable is angular momentum.
We know that even a single electron in a hydrogen atom generally has orbital angular momentum L (with (2 l + 1) possible orientations where l is a integer) and spin angular momentum S (with two possible orientations commonly described as spin up and spin down or s = ± 1/2). In more complicated atoms there may be many components of angular momentum; for example, the helium atom has two electrons both of which have orbital and spin angular momenta. Also, in many atomic systems of physical interest we need to know how to combine angular momenta. This chapter explains how to do it.