Translational states, of atoms

The Englishversionof Volume II of Brauer s Handbook follows the path of the very well received translation of Volume I. Again, some of the material and particularly the bibliography has been corrected and brought up to date. The nomenclature has been revised where necessary, with the Stock and the Stock-Werner systems (the practice of using Roman numerals to define oxidation states of atoms) adopted as much as possible. This conforms with current I.U. P. A. C. and Chemical Abstracts practice [for details of this, see Robert C. Brasted, J. Chem. Education 35, 136 (1948)]. The references to laboratory equipment and techniques reflect current U. S. usage, but useful European methods have been retained. 

For atomic and molecular systems, we actually have such expressions They come from the application of quantum mechanics to the translations, rotations, vibrations, and electronic states of atoms and molecules. Admittedly, Boltzmann didn t have quantum mechanics, because he developed the rudiments of statistical mechanics about 50 years before quantum mechanics was formulated. In fact, some ofhis expressions are incorrect by not including Planclfs constant (Boltzmann was unaware of its existence for most ofhis life). But in the calculation of thermodynamic values, the Planck s constants cancel. Their omission was, ultimately, unnoticed. However, in the material to come, we will use the quantum-mechanical basis of energy levels. 

Translational, Rotational, and Vibrational States of Atoms and Molecules... 

Electronic spectroscopy is the study of transitions, in absorption or emission, between electronic states of an atom or molecule. Atoms are unique in this respect as they have only electronic degrees of freedom, apart from translation and nuclear spin, whereas molecules have, in addition, vibrational and rotational degrees of freedom. One result is that electronic spectra of atoms are very much simpler in appearance than those of molecules. 

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