Hyperfine structure measurements of antiprotonic ³He using microwave spectroscopy

Zielsetzung dieses Projekts war die Messung der Hyperfeinstruktur von antiprotonischem 3He mittels Laser-Mikrowellen-Laser Spektroskopie. Antiprotonisches Helium ist ein neutrales, exotisches Atom, bestehend aus einem Heliumkern, einem Elektron und einem Antiproton. Die Wechselwirkungen der einzelnen Drehmomente erzeugen eine Hyperfeinaufspaltung (HFS) innerhalb der Energiezustände. Die 3% der gebildeten Atome antiprotonischen Heliums, die in einem metastabilen, durch Strahlung zerfallenden Zustand verbleiben, haben eine Lebensdauer von 1-3 Mikrosekunden. Das dadurch definierte Zeitfenster wird genützt, um mikrowellen-spektroskopische Messungen durchzuführen. Die Hyperfeinstruktur von antiprotonischem 4He wurde bereits vollständig untersucht. Mit diesen Messungen kann man das magnetische Moment des Antiprotons bestimmen. Der Vergleich des magnetischen Moments für Proton und Antiproton gibt Aufschluss über eine mögliche CPT-Verletzung. Die komplexere Struktur von antiprotonischem 3He ermöglicht eine Gegenprüfung dieser Ergebnisse sowie einen restriktiveren Test der theoretischen Berechnungen. Das Prinzip der Messung basiert darauf eine Laser-induzierte Asymmetrie zwischen den Besetzungsniveaus der HF Zustände zu erzeugen. Danach wird mit Hilfe von Mikrowellenstrahlung ein Besetzungsübergang zwischen diesen Zuständen stimuliert und darauffolgend ein weiterer Laserpuls gesendet, um die erfolgte Besetzungsänderung zu messen. Mehrere kryogenische Kavitäten wurden simuliert, gebaut und getestet. Ein wesentlicher Teil meiner Arbeit bestand darin Berechnungen und finite-element Simulationen dazu durchzuführen ebenso wie umfangreiche Tests, Diagnostik und Kalibrierung dieser Hochfrequenzstrukturen und des gesamten Mikrowellen-Aufbaus. Der Fokus meines Projekts war die Umsetzung der spektroskopischen und die anschliessende Datenanalyse sowie numerische Simulationen der Übergänge zwischen den Hyperfeinzuständen. Die gemessenen Werte für diese beiden Übergangsfrequenzen sind 11.125 48(08) GHz und 11.157 93(13) GHz.The goal of this project was to measure the hyperfine structure of antiprotonic 3He using the technique of laser-microwave-laser spectroscopy. Antiprotonic helium is a neutral exotic atom, consisting of a helium nucleus, an electron and an antiproton. The interactions of the angular momenta of its constituents cause a hyperfine splitting (HFS) within the energy states of this new atom. The 3% of formed antiprotonic helium atoms remain in a metastable, radiative decay-dominated state with a lifetime of 1-3 microseconds. The hyperfine structure of antiprotonic 4He was already extensively investigated before and the spin magnetic moment of the antiproton was determined. A comparison of the result to the proton magnetic moment provides a test of CPT invariance. Due to its higher complexity the new exotic three-body system of is a cross-check for the measurements with antiprotonic 4He and a more stringent test of theory. The measurement principle is based on inducing a population asymmetry by laser-depopulation of one of two HF states. Subsequently, a microwave pulse stimulates population transfer between these substates, followed by a second laser pulse to measure the transferred population. Several cryogenic cavities were designed, built and tested. One major part of my work consisted of calculations and finite-element simulations as well as detailed preparation studies, diagnostics and calibration of the complete microwave apparatus. The main focus was on the execution of the and the related data analysis. The final results for the two measured transition frequencies are 11.125 48(08) GHz and 11.157 93(13) GHz

Microwave spectroscopic study of the hyperfine structure of antiprotonic helium-3

In this work we describe the latest results for the measurements of the hyperfine structure of antiprotonic helium-3. Two out of four measurable super-super-hyperfine SSHF transition lines of the (n,L)=(36,34) state of antiprotonic helium-3 were observed. The measured frequencies of the individual transitions are 11.12548(08) GHz and 11.15793(13) GHz, with an increased precision of about 43% and 25% respectively compared to our first measurements with antiprotonic helium-3 [S. Friedreich et al., Phys. Lett. B 700 (2011) 1--6]. They are less than 0.5 MHz higher with respect to the most recent theoretical values, still within their estimated errors. Although the experimental uncertainty for the difference of 0.03245(15) GHz between these frequencies is large as compared to that of theory, its measured value also agrees with theoretical calculations. The rates for collisions between antiprotonic helium and helium atoms have been assessed through comparison with simulations, resulting in an elastic collision rate of gamma_e = 3.41 +- 0.62 MHz and an inelastic collision rate of gamma_i = 0.51 +- 0.07 MHz.Comment: 15 pages, 9 figures. arXiv admin note: substantial text overlap with arXiv:1102.528

Hyperfine Structure Measurements of Antiprotonic 3^3He using Microwave Spectroscopy

The goal of this project was to measure the hyperfine structure of $\overline{\text{p}}^3$He$^+$ using the technique of laser-microwave-laser spectroscopy. Antiprotonic helium ($\overline{\text{p}}$He$^+$) is a neutral exotic atom, consisting of a helium nucleus, an electron and an antiproton. The interactions of the angular momenta of its constituents cause a hyperfine splitting ({HFS}) within the energy states of this new atom. The 3\% of formed antiprotonic helium atoms which remain in a metastable, radiative decay-dominated state have a lifetime of about 1-3~$\mu$s. This time window is used to do spectroscopic studies. The hyperfine structure of $\overline{\text{p}}^4$He$^+$ was already extensively investigated before. From these measurements the spin magnetic moment of the antiproton can be determined. A comparison of the result to the proton magnetic moment provides a test of {CPT} invariance. Due to its higher complexity the new exotic three-body system of $\overline{\text{p}}^3$He$^+$ is a cross-check for the measurements with $\overline{\text{p}}^4$He$^+$ and a more stringent test of theoretical calculations and methods. The measurement principle is based on inducing a population asymmetry by laser-depopulation of one of two {HF} states. Subsequently, a microwave pulse stimulates population transfer between these substates, followed by a second laser pulse to measure the transferred population. For the microwave spectroscopy several cryogenic cavities were designed, built and tested. One major part of my work consisted of calculations and finite-element simulations as well as detailed preparation studies, diagnostics and calibration of these high frequency structures and the complete microwave apparatus. The main focus of my thesis was on the execution of the measurements at {CERN} (as well as the organization or the supervision of project students) and the related data analysis, including numerical simulations of the hyperfine transition processes. Two out of four measurable transition lines of the $(n,L)=(36,34)$ state of $\overline{\text{p}}^3$He$^+$ were observed for the first time and in good agreement with theoretical {QED} calculations. The final results for the two measured transition frequencies are $\nu_{\text{HF}}^{--} = 11.125 48(08)$~GHz and $\nu_{\text{HF}}^{-+} = 11.157 93(13)$~GHz

Two-photon laser spectroscopy of antiprotonic helium and the antiproton-to-electron mass ratio

Physical laws are believed to be invariant under the combined transformations of charge, parity and time reversal (CPT symmetry). This implies that an antimatter particle has exactly the same mass and absolute value of charge as its particle counterpart. Metastable antiprotonic helium is a three-body atom consisting of a normal helium nucleus, an electron in its ground state and an antiproton occupying a Rydberg state with high principal and angular momentum quantum numbers, respectively n and l, such that n~l+1 ~ 38. These atoms are amenable to precision laser spectroscopy, the results of which can in principle be used to determine the antiproton-to-electron mass ratio and to constrain the equality between the antiproton and proton charges and masses. Here we report two-photon spectroscopy of antiprotonic helium, in which two antiprotonic helium isotopes are irradiated by two counter-propagating laser beams. This excites nonlinear, two-photon transitions of the antiproton of the type (n,l) -> (n-2, l-2) at deep-ultraviolet wave-lengths (139.8, 193.0 and 197.0 nm), which partly cancel the Doppler broadening of the laser resonance caused by the thermal motion of the atoms. The resulting narrow spectral lines allowed us to measure three transition frequencies with fractional precisions of 2.3–5 parts in 10^9. By comparing the results with three-body quantum electrodynamics calculations, we derived an antiproton-to-electron mass ratio of 1,836.1526736(23), where the parenthetical error represents one standard deviation. This agrees with the proton-to-electron value known to a similar precision