Fundamental Symmetries and Symmetry Violations from High Resolution Spectroscopy

Abstract

AbstractAfter an introductory survey, we introduce the seven fundamental symmetries of physics in relation to the group of the molecular Hamiltonian and the current standard model of particle physics (SMPP). We discuss the relation of these symmetries to conservation laws and fundamentally nonobservable properties of nature with the example of parity violation. The particular importance of experiments on detecting symmetry breakings is outlined and the three distinct, basic concepts of symmetry breaking (spontaneous,de facto,de lege) are illustrated with the example of space inversion symmetry breaking and parity violation in chiral molecules. Similar conceptual situations are found for our understanding of the underlying physics of molecular chirality by various types of symmetry breakings, of the evolution of biomolecular homochirality and of irreversibility as breaking of time reversal symmetry. The current status of the quantitative theory of molecular parity violation in the framework of electroweak quantum chemistry is reviewed, including the change of order of magnitude, which was found in recent years and has since been confirmed repeatedly.The concepts of high‐resolution spectroscopic experiments on parity violation in chiral molecules are discussed and the status of current attempts toward detecting molecular parity violation is summarized with particular emphasis on the possibilities of measuring time‐dependent parity violation in the exceptional (still hypothetical) unstable parity isomers of chiral molecules. The concept of successive symmetry breakings in the quantum dynamics of molecules is illustrated with the wide range of time‐scales for symmetry‐breaking processes ranging from femtoseconds in experiments on very fast intramolecular vibrational redistribution (IVR) to the theoretical times of seconds for molecular parity violation.The role of approximate symmetries and conservation laws for our understanding of selection rules in spectroscopy and in chemical reaction dynamics is analyzed in some detail with the example of approximate parity and nuclear spin symmetry conservation in radiative and reactive molecular processes. This includes the use of permutation‐inversion symmetry groups in applications to spectroscopy and state‐selected chemical reactions. Statistical concepts for the description of molecular energy levels are presented for use in high‐resolution spectroscopy and chemical reactions in relation to symmetry properties.We conclude with a summary of the current status of the following symmetries and their violations in spectroscopy and molecular dynamics: nuclear spin symmetry in chemical processes, space inversion symmetry and parity violation in chiral molecules, time reversal symmetry in intramolecular processes, and combined charge conjugation, parity, and time reversal (CPT) symmetry in relation to more fundamental aspects of time reversal and speculations on mass differences in chiral molecules and chiral neutrinos and their antimatter counterparts.