Theory of Atomic Spectroscopy

C.W. HAIGH, The theory of atomic spectroscopy jj coupling, intermediate coupling and configuration interaction. J. Chem. Educ., 72, 206 (1995). 

The present book is designed to describe the basic theory of atomic spectroscopy, instrumentation, techniques, and the application of various analytical atomic spectrometric methods (AAS, plasma AES, AFS, and ICP-MS). 

The need for and use of thermal energy as outlined above has resulted in the invention of a number of separate and distinctly different atomizer and instrument designs, albeit based on the same theory, under the heading of atomic spectroscopy. 

Discuss the fundamental theory of Emission Spectroscopy . Substantiate your explanation based on the energy-level diagrams for an atom and a molecule . 

This monograph presents a complete, up-to-date guide to the theory of modern spectroscopy of atoms. It describes the contemporary state of the theory of many-electron atoms and ions, the peculiarities of their structure and spectra, the processes of their interaction with radiation, and some of the applications of atomic spectroscopy. 

The data of atomic spectroscopy are of extreme importance in revealing the nature of quantum-electrodynamical effects. For the investigation of many-electron atoms and ions, it is of great importance to combine theoretical and experimental methods. Therefore, the methods used must be universal and accurate. A number of physical characteristics of the many-electron atom (e.g., a complete set of quantum numbers) may be found only on the basis of theoretical considerations. In many cases the mathematical modelling of physical objects and processes using modern computers may successfully replace the corresponding experiments. In this book we shall describe the contemporary state of the theory of many-electron atoms and ions, the peculiarities of their structure and spectra as well as the processes of their interaction with radiation, and some applications. 

A basic understanding of the quantum theory is essential in many areas of chemistry, especially in connection with spectroscopy and with theories of atomic and molecular structure. The present book gives an introduction to the theory, and its application to elementary atomic structure, but chemical bonding is not discussed. I have tried to put the essential ideas in their historical context, but without retaining the historical introduction which has been traditional with this topic. With the crucial and difficult concepts of wave-particle duality, it seemed to me more important to give modem illustrations to show that they have current applications in chemistry. 

Robinson, J. W., Theory of Atomic Absorption and Fluorescence Spectroscopy, Academic Press, 1974. 

The problem of N bound electrons interacting under the Coulomb attraction of a single nucleus is the basis of the extensive field of atomic spectroscopy. For many years experimental information about the bound eigenstates of an atom or ion was obtained mainly from the photons emitted after random excitations by collisions in a gas. Energy-level differences are measured very accurately. We also have experimental data for the transition rates (oscillator strengths) of the photons from many transitions. Photon spectroscopy has the advantage that the photon interacts relatively weakly with the atom so that the emission mechanism is described very accurately by first-order perturbation theory. One disadvantage is that the accessibility of states to observation is restricted by the dipole selection rule. 

When applied to hydrogen, Bohr s theory worked well when atoms with more electrons were considered, the theory failed. Complications such as elliptical rather than circular orbits were introduced in an attempt to fit the data to Bohr s theory. The developing experimental science of atomic spectroscopy provided extensive data for testing of the Bohr theory and its modifications and forced the theorists to work hard to explain the spectroscopists observations. In spite of their efforts, the Bohr theory eventually proved unsatisfactory the energy levels shown in Figure 2-2 are valid only for the hydrogen atom. An important characteristic of the electron, its wave nature, still needed to be considered. 

In order to introduce the theory of vibrational spectroscopy in inelastic neutron scattering, we make some simplifications that will help us to understand the concepts. First we shall deal with the vibrational modes of molecules in a vacuum or in a dilute gas phase. Note, however, that in INS experiments the sample is cooled to ca 20 K, therefore the molecules are part of an extended solid. However, because the forces that keep the atoms in the molecule are often larger than the forces that molecules experience from other molecules in the condensed phase, isolated molecule calculations can be good models. 

Symposia (Many-Body Theory of Atomic Systems, 1979, and Heavy-ion Spectroscopy and QED Effects in Atoms, 1992) and one ICAP conference (Gdteborg 1982). Ingvar has been an invited speaker and session chairman at innumerable scientific conferences all over the world. 

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