Preprint Review Version 1 Preserved in Portico This version is not peer-reviewed

Fundamentals of Diatomic Molecular Spectroscopy

Version 1 : Received: 19 September 2021 / Approved: 20 September 2021 / Online: 20 September 2021 (10:45:08 CEST)

A peer-reviewed article of this Preprint also exists.

Parigger, C.G. Fundamentals of Diatomic Molecular Spectroscopy. Foundations 2021, 1, 208-216. Parigger, C.G. Fundamentals of Diatomic Molecular Spectroscopy. Foundations 2021, 1, 208-216.


The interpretation of optical spectra requires thorough comprehension of quantum mechanics, especially understanding the concept of angular momentum operators. Suppose now that a transformation from laboratory-fixed to molecule-attached coordinates, by invoking the correspondence principle, induces reversed angular momentum operator identities. However, the foundations of quantum mechanics and the mathematical implementation of specific symmetries assert that reversal of motion or time reversal includes complex conjugation as part of anti-unitary operation. Quantum theory contraindicates sign changes of the fundamental angular momentum algebra. Reversed angular momentum sign changes are of heuristic nature and are actually not needed in analysis of diatomic spectra. This work addresses sustenance of usual angular momentum theory, including presentation of straightforward proofs leading to falsification of the occurrence of reversed angular momentum identities. This review also summarises aspects of a consistent implementation of quantum mechanics for spectroscopy with selected diatomic molecules of interest in astrophysics and in engineering applications.


Foundations of Quantum Mechanics; Molecular Spectroscopy; Diatomic Molecules; Symmetry Transformations; Optical Emission Spectroscopy; Astrophysics


Physical Sciences, Atomic and Molecular Physics

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