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SYQM: Symposium Precise Quantum Molecules
SYQM 1: Precise Quantum Molecules
SYQM 1.3: Hauptvortrag
Donnerstag, 11. September 2025, 11:45–12:15, ZHG105
High-resolution spectroscopy of molecular ions — •Stephan Schlemmer — I. Physikalisches Institut, Universität zu Köln
Spectroscopy is one of the foundations of quantum mechanics. For molecules the spectra usually break-up into the electronic, vibrational and rotational energy regime based on the Born-Oppenheimer approximation which separates the dynamics of the electrons from those of the nuclei. Vibrational spectra reveal the forces between the atoms constituing the molecule and rotational spectra are related to their mass distribution, i.e., the structure of the molecule and highly precise distances of the atomic nuclei. These findings lead to our today’s picture of a molecule as a set of atoms (balls) bound by their electrons (sticks), where, e.g., the methane molecule, CH4, has a pyramidal structure of the hydrogens with the carbon atom in the center entertaining one bond to each of the hydrogens. As a result of this success story of quantum mechanics complex molecules are found in space based on their fingerprint like spectra. I will present example spectra for molecular ions which have been discovered recently and which play an important role in interstellar chemistry. However, several well bond molecules are very floppy, meaning the nuclei undergo large amplitude motions and the picture of a molecular structure described above is called in question. Finding a proper quantum mechanical description for such systems as well as measuring their spectra is still a challenge today as will be discussed in this work.