E-Book Overview
This three-volume encyclopedia offers extensive coverage in the closely related areas of chemical physics and physical chemistry. Focusing on both disciplines as interrelated, the Encyclopedia contains a wide variety of information to meet the special research needs of the chemical physicist and the physical chemist and, thus, enables specialists in both fields to conduct interdisciplinary research. Features include definitions of the scope of each subdiscipline and instructions on where to go for a more complete and detailed explanation. The Encyclopedia is also a helpful resource for graduate students because it gives a synopsis of the basics and an overview of the range of activities in which physical principles are applied to chemical problems.
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-1- A1.1 The quantum mechanics of atoms and molecules John F Stanton A1.1.1 INTRODUCTION At the turn of the 19th century, it was generally believed that the great distance between earth and the stars would forever limit what could be learned about the universe. Apart from their approximate size and distance from earth, there seemed to be no hope of determining intensive properties of stars, such as temperature and composition. While this pessimistic attitude may seem quaint from a modern perspective, it should be remembered that all knowledge gained in these areas has been obtained by exploiting a scientific technique that did not exist 200 years ago—spectroscopy. In 1859, Kirchoff made a breakthrough discovery about the nearest star—our sun. It had been known for some time that a number of narrow dark lines are found when sunlight is bent through a prism. These absences had been studied systematically by Fraunhofer, who also noted that dark lines can be found in the spectrum of other stars; furthermore, many of these absences are found at the same wavelengths as those in the solar spectrum. By bu