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 …

Abstract The Antiproton Decelerator (AD) facility of CERN began operation in 1999 to serve
experiments for studies of CPT invariance by precision laser and microwave spectroscopy of …

We have measured the 1 S–2 S transition frequency in atomic hydrogen via two-photon
spectroscopy on a 5.8 K atomic beam. We obtain f 1 S–2 S= 2 466 061 413 187 035 (10) Hz …

We present a measurement of the hydrogen 2 S 1/2-8 D 5/2 transition performed with a
cryogenic atomic beam. The measured resonance frequency is ν= 770 649 561 570.9 (2.0) …

The field of experimental positronium physics has advanced significantly in the last few
decades, with new areas of research driven by the development of techniques for trap** …

We report a new measurement of the positronium (Ps) 2 S 3 1→ 2 P 3 0 interval. Slow Ps
atoms, optically excited to the radiatively metastable 2 S 3 1 level, flew through a microwave …

We report a new measurement of the n= 2 Lamb shift in Muonium. Our result of 1047.2 (2.3)
stat (1.1) syst MHz comprises an order of magnitude improvement upon the previous best …

We present a new experiment, Mu-MASS, aiming for a 1000-fold improvement in the
determination of the 1S-2S transition frequency of Muonium (M), the positive-muon/electron …

The 1 S-2 S two-photon transition in singly ionized helium is a highly interesting candidate
for precision tests of bound-state quantum electrodynamics (QED). With the recent advent of …

We generated a series of harmonics in a xenon gas jet inside a cavity seeded by pulses
from a Ti: sapphire mode-locked laser with a repetition rate of 10.8 MHz. Harmonics up to …