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...

We have performed two-photon ultraviolet direct frequency comb spectroscopy on the 1S-3S transition in atomic hydrogen to illuminate the so-called proton radius puzzle and to demonstrate the potential of this method. The proton radius puzzle is a significant discrepancy between data obtained with muonic hydrogen and regular atomic hydrogen that could not be explained within the framework of quantum electrodynamics. By combining our result [f1S-3S = 2,922,743,278,665.79(72) kilohertz] with a previous measurement of the 1S-2S transition frequency, we obtained new values for the Rydberg constant [R∞ = 10,973,731.568226(38) per meter] and the proton charge radius [rp = 0.8482(38) femtometers]. This result favors the muonic value over the world-average data as presented by the most recent published CODATA 2014 adjustment.

We propose and demonstrate a new scheme for atom interferometry, using light pulses inside an optical cavity as matter wave beamsplitters. The cavity provides power enhancement, spatial filtering, and a precise beam geometry, enabling new techniques such as low power beamsplitters (< 100 µW), large momentum transfer beamsplitters with modest power, or new self-aligned interferometer geometries utilizing the transverse modes of the optical cavity. As a first demonstration, we obtain Ramsey-Raman fringes with > 75% contrast and measure the acceleration due to gravity, g, to 60 µg/ √ Hz resolution in a Mach-Zehnder geometry. We use > 10 7 cesium atoms in the compact mode volume (600 µm 1/e 2 waist) of the cavity and show trapping of atoms in higher transverse modes. This work paves the way toward compact, high sensitivity, multi-axis interferometry.In a light-pulse atom interferometer, recoils from photon-atom interactions are used to split and interfere matter waves (see Fig. 1). These interferometers have been used to measure the gravitational acceleration g [1], rotation Ω [2], gravity gradients [3], the fine structure constant [4], Newton's gravitational constant [5,6], and absolute masses in a proposed revision of the SI [7,8]; to test Einstein's equivalence principle [9][10][11][12]; and have been proposed to measure the free fall of antimatter [13] and to detect gravitational waves [14][15][16]. The sensitivity of a conventional Mach-Zehnder interferometer increases with the measured phase difference(1) (where v 0 is the initial velocity of the atom), which scales with the pulse separation time T and the recoil momentum p =h k eff , where k eff is the effective wavenumber of the photons. State of the art atom interferometers are limited by several engineering boundaries. T is limited by the free-fall time in atomic fountains, which are now as high as 10 m [17,18]. Multiphoton interactions can increase the recoil momentum to a multiple nhk of the single photon recoil [19][20][21][22][23] but are limited by the available laser power (e.g. 6 W in [24], 43 W in [25]). Finally, wavefront distortions spread the local wavevector around its mean, lowering interference contrast and reducing both sensitivity and accuracy. An optical cavity can solve these problems by providing spatial filtering to clean the wavefronts and enhancing laser intensity. However, running an atom interferometer inside an optical cavity presents challenges in keeping the atoms in the relatively small cavity mode volume and having multiple laser frequencies (needed due to recoil frequency shifts, Doppler shifts, and atomic structure) simultaneously resonant with the cavity. Here, we present a cesium atom interferometer inside an in-vacuum optical cavity and demonstrate gravity measurements using less than 100µW of laser power incident on the cavity.The use of an optical cavity has many advantages. First, laser power limits interferometers using both large momentum transfer beamsplitters and optical lattices. is modulated at the hyperfine frequ...

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We give a pedagogical description of the method to extract the charge radii and Rydberg constant from laser spectroscopy in regular hydrogen (H) and deuterium (D) atoms, that is part of the CODATA least-squares adjustment (LSA) of the fundamental physical constants. We give a deuteron charge radius r d from D spectroscopy alone of 2.1415(45) fm. This value is independent of the measurements that lead to the proton charge radius, and five times more accurate than the value found in the CODATA Adjustment 10. The improvement is due to the use of a value for the 1S → 2S transition in atomic deuterium which can be inferred from published data or found in a PhD thesis.One could thus argue that the CODATA deuteron charge radius is larger than the muonic deuterium value only because the correlated, and very accurately determined, proton charge radius is larger than the muonic hydrogen value.Here we use the available data on spectroscopy of atomic deuterium to deduce a precise value of r d which does not depend on r p through Eq. (5). In our analysis we use a value of the 1S → 2S transition in atomic deuterium (see Tab. VI) that has not been used by CODATA. Its value can either be inferred from published data or found in a PhD thesis [10]. This 1S → 2S value helps improve the accuracy of the deuteron charge radius by a factor of five, compared to the CODATA Partial Adjustment 10 [3]. A. CODATA Partial AdjustmentsThe final CODATA-2010 recommended values of the fundamental constants are deduced in the so-called "Adjustment 3". As detailed in Sec. XIII.B.2 on page 1577 ff. of the CODATA-2010 report [3], there are additional adjustments that use only a subset of the available input data. "Adjustments 6-12" are the ones relevant for r p , r d and the Rydberg constant R ∞ , and the results are summarized in Tab. XXXVIII of Ref. [3].These auxiliary Partial Adjustments serve two purposes: On the one hand, they verify the internal consistency of the CODATA LSA, as results from different subsets of the data are in good agreement with each other. On the other hand,