Dokument: High-accuracy laser spectroscopy of the molecular hydrogen ion H_{2}^{+}
| Titel: | High-accuracy laser spectroscopy of the molecular hydrogen ion H_{2}^{+} | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=70141 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20250714-105723-8 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Schenkel, Magnus Roman [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Ph.D. Schiller, Stephan [Gutachter] Prof. Dr. Görlitz, Axel [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 530 Physik | |||||||
| Beschreibung: | To explore the limits of contemporary knowledge is a prime objective of studies in fundamental physics. The group of systems of molecular hydrogen ions (MHIs) offers many prospects in this regard: From spectroscopic data, one may extract fundamental constants or test theoretical predictions. MHI spectroscopy, in particular that of HD^{+}, has undergone exceptional progress in recent years. A key achievement has been the recent determination of the ratio of its reduced nuclear mass to the electron mass with state-of-the-art precision.
However, in order to extract generally applicable constants from spectroscopic data of HD^{+}, such as the proton-electron mass ratio, it is necessary to combine it with data from other experiments. In particular, the deuteron-proton mass ratio, obtained from cyclotron frequency measurements in Penning traps. To avoid this dependency and obtain purely spectroscopic values, an alternative approach is to measure transition frequencies in the closely related molecule H_{2}^{+}. But, despite its unique status as the simplest molecule in the universe, the highly accurate measurements necessary for such an endeavor have so far remained elusive, due to the experimental challenges posed by H_{2}^{+}. This thesis will demonstrate how these challenges can be overcome through the development of a capable spectroscopy laser system and its integration into a spectroscopy apparatus with a linear radio-frequency ion trap at its core. The laser system is characterized and found to have a relative frequency stability of better than 1*10^{-14} over timescales between 1 and 10^{7} seconds, coupled with a frequency accuracy relative to the SI second of a similar magnitude. Its output power is at the watt-level; sufficiently high in order to drive electric-quadrupole transitions in molecular hydrogen ions. The combination of the spectroscopy laser and the ion trap allows for two spectroscopic studies based on laser excitation of H_{2}^{+} to be performed. The initial study encompasses the observation of a Doppler-broadened rovibrational transition in H_{2}^{+}, thereby achieving an experimental objective that was envisioned decades ago. This observation is accompanied by the first study of systematic effects on an electric-quadrupole transition in a molecular ion, specifically of Doppler-free single Zeeman components in HD^{+}. These results represent only the second time that an electric-quadrupole transition has been observed in a molecular ion, but with a precision that is a factor \sim10^{6} greater than that of the first observation. The study demonstrates that achieving ultra-high accuracy for this type of transition is a realistic prospect. The second study improves the H_{2}^{+}-result, surpassing the Doppler-effect and achieving a relative accuracy of the transition frequency of 8*10^{-12}. This represents the most accurate measurement of any H_{2}^{+} property to date, exhibiting a factor of \simeq10^{3} improvement over the previous record. The obtained line resolution also surpasses the highest resolution achieved with HD^{+}. By combining the measurement with theory and constants obtained from hydrogen spectroscopy, the proton-electron mass ratio is derived with an accuracy similar to that of the current CODATA standard and independent of Penning trap mass spectrometry. It is the first time that this fundamental mass ratio has been derived from spectroscopic data alone. The values for the mass ratio, obtained through different experiments and theories, are in agreement. Furthermore, the result may be combined with HD^{+} data in order to yield the deuteron-proton mass ratio with similar accuracy. Alternatively, the measurements can be compared with theory to result in a test of the underlying theoretical framework, where agreement is found at a relative level of 8*10^{-12}, representing one of the most accurate experiment-theory comparisons in physics. The work introduces precision spectroscopy of H_{2}^{+} into the field of fundamental physics. The results demonstrate that ultra-high accuracy spectroscopy of transition frequencies of molecular hydrogen ions, specifically of electric-quadrupole transitions, has the potential to become a new standard for the metrology of fundamental constants. Furthermore, this work lays the experimental foundation of a vision proposed decades ago: the comparison of H_{2}^{+} with its antimatter counterpart, the anti-molecule \overline{\text{H}_{2}}^{-}. | |||||||
| Lizenz: |  Dieses Werk ist lizenziert unter einer Creative Commons Namensnennung 4.0 International Lizenz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Physik » Experimentalphysik | |||||||
| Dokument erstellt am: | 14.07.2025 | |||||||
| Dateien geändert am: | 14.07.2025 | |||||||
| Promotionsantrag am: | 11.12.2024 | |||||||
| Datum der Promotion: | 06.06.2025 |
