The Rydberg constant and proton size from atomic hydrogen

Abstract

ZusammenfassungDas Wasserstoffatom (H) stellt ein einzigartiges System für Tests der Quanten-Elektrodynamik dar. Aufgrund seiner einfachen Struktur und genauen theoretischen Beschreibung liefert es außerdem wichtige Daten für die Bestimmung der RydbergKonstante R ∞ und des Proton-Ladungsradius r p im Rahmen der globalen Anpassung fundamentaler Konstanten durch das Committee on Data for Science and Technology (CODATA). Im Jahre 2010 kam das sogenannte "proton size puzzle" auf, eine Diskrepanz von sieben Standardabweichungen zwischen CODATA und dem zehn mal genauer gemessenen Wert von r p in myonischem Wasserstoff (µ -p, [1, 2] AbstractThe hydrogen atom (H) is a unique system for tests of quantum electrodynamics (QED). Due to its simplicity and accurate theoretical description, it also provides key input data for the determination of the Rydberg constant R ∞ and the proton root mean square (r.m.s.) charge radius r p in the global adjustment of fundamental constants [4] by the Committee on Data for Science and Technology (CODATA). In the year 2010, the "proton size puzzle" emerged, which refers to a discrepancy of seven standard deviations between CODATA and a ten times more accurate measurement of r p in muonic hydrogen (µ -p, [1, 2]). Proposed solutions for this puzzle cover a wide range of scenarios, up to physics beyond the standard model [3]. This thesis reports on a novel scheme for high resolution spectroscopy of dipole allowed 2S -nP transitions in H, using a cryogenic beam of H atoms that are prepared in the meta-stable 2S F =0 1/2 state by state selective optical excitation. Such measurements can be used for a new determination of R ∞ and r p from H spectroscopy, shedding new light on the "proton size puzzle". The scheme has been applied to spectroscopy of the 2S-4P transition first, yielding: These values are as accurate as the ones determined from the aggregate world data of precision H spectroscopy (15 measurements) that enter the CODATA adjustment. While a discrepancy of 3.8 combined standard deviations is found to the latter, the presented results agree with the measurements in µ -p. The 2S-4P experiment is essentially unaffected by the systematic effects dominating the uncertainties in the previous most precise determinations of R ∞ using dipole forbidden two photon transitions in H. Instead, the main systematic effects are the first order Doppler effect, canceled by the use of an active fiber-based retroreflector (AFR) developed in this thesis, and line shape distortions due to quantum interference (QI) of neighboring atomic resonances. The latter effect has come to the attention of the precision spectroscopy community only recently [8,9]. Apparent QI line shifts have been studied experimentally, yielding the first direct observation in precision spectroscopy of largely separated atomic resonances. The observed shifts of up to ± 51 kHz are six times larger than the proton size discrepancy for the 2S-4P transition. They are brought under control by a suitable line shape model function, derived and...

Experimental progress in positronium laser physics

“…The measurements that, taken in conjunction with the precision 1S-2S data [491], give the proton radius are shown in Figure 43 [614]. These include microwave Lamb shift [605] measurements [619,620] performed using the separated oscillatory field method of Ramsay [621], as well as optical 2S-nS/D transitions in hydrogen [161,162,610,[622][623][624]) (for some reason, always with even values of n).…”

“…Recently a measurement of the 2S-4P transition in hydrogen [614] has revealed the existence of a possible systematic shift that may mean that the Rydberg constant derived from hydrogen spectroscopy is the source of the discrepancy, as indicated in Figure 43. However, more measurements are required to verify if this is really the case.…”

Producing long-lived 23S positronium via 33P laser excitation in magnetic and electric

“…As a matter of fact, the Ps energy levels can be calculated as a perturbative series in powers of α with very high precision, only limited by the knowledge of the fundamental constants [3]. Hence, Ps offers a great advantage with respect to analogous calculations and experiments on hydrogen, for example, because in this case QED predictions require a precise knowledge of the proton finite-size effects [2,4], which are increasingly important in H spectroscopy.…”

“…Some experimental tests are based on precision laser spectroscopy [4], in particular exploiting the two-photon Dopplerfree transition 1 3 …”

Improving the accuracy of the muon mass and magnetic moment anomaly via the bound-muon g factor

“…Recently, high-precision spectroscopy experiments with the muonic H atom yielded a value for the proton radius which strongly disagrees with that obtained from measurements on regular H [5,6] (see also [7]). Experiments aiming at an improved determination of muon properties can help clarify both issues and provide insight into speculative new physics.…”