Observation of the 1S–2P Lyman-α transition in antihydrogen

Abstract

In 1906, Theodore Lyman discovered his eponymous series of transitions in the extreme-ultraviolet region of the atomic hydrogen spectrum1,2. The patterns in the hydrogen spectrum helped to establish the emerging theory of quantum mechanics, which we now know governs the world at the atomic scale. Since then, studies involving the Lyman-α line—the 1S–2P transition at a wavelength of 121.6 nanometres—have played an important part in physics and astronomy, as one of the most fundamental atomic transitions in the Universe. For example, this transition has long been used by astronomers studying the intergalactic medium and testing cosmological models via the so-called ‘Lyman-α forest’3 of absorption lines at different redshifts. Here we report the observation of the Lyman-α transition in the antihydrogen atom, the antimatter counterpart of hydrogen. Using narrow-line-width, nanosecond-pulsed laser radiation, the 1S–2P transition was excited in magnetically trapped antihydrogen. The transition frequency at a field of 1.033 tesla was determined to be 2,466,051.7 ± 0.12 gigahertz (1σ uncertainty) and agrees with the prediction for hydrogen to a precision of 5 × 10−8. Comparisons of the properties of antihydrogen with those of its well-studied matter equivalent allow precision tests of fundamental symmetries between matter and antimatter. Alongside the ground-state hyperfine4,5 and 1S–2S transitions6,7 recently observed in antihydrogen, the Lyman-α transition will permit laser cooling of antihydrogen8,9, thus providing a cold and dense sample of anti-atoms for precision spectroscopy and gravity measurements10. In addition to the observation of this fundamental transition, this work represents both a decisive technological step towards laser cooling of antihydrogen, and the extension of antimatter spectroscopy to quantum states possessing orbital angular momentum.

Simulations of Majorana spin flips in an antihydrogen trap

“…Because the trap depth is only ∼ 1 2 k B K and theHs are formed at much higher temperatures, the distribution of atoms is approximately a flat distribution in velocity space within a sphere corresponding to a kinetic energy of ≃ 1 2 k B K leading to a normalized distribution with respect to speed of P (v) = 3v 2 /v 3 max . This distribution gives good agreement with measurements [13,21]. From these parameters, we can estimate the rate for a spin flip process with cross…”

Gravitational Weakening of Seismic Origin as a Driving Mechanism of Some Astronomical Anomalies

“…It is probable that during quakes, the hydrogen electrons are excited to higher energy levels. As the electrons decay to the lowest energy level, they emit ultraviolet light to form the Lyman Series (Ahmadi et al, 2018). The ULF radiation, with wavelengths of about 280nm, has the right energy magnitude that can ionize hydrogen atoms in space.…”

Rabi Experiments on the σ and π Hyperfine Transitions in Hydrogen and Status of ASACUSA’s Antihydrogen Program

“…The majority of experiments in this area compare antimatter properties to those of their matter counterparts for a precise test of CPT symmetry. Recent results on the magnetic moment of the antiproton 1 by BASE as well as the 1S-2S, 2 1S-2P, 3 and hyperfine transitions 4 of antihydrogen (H) by ALPHA 5 demonstrate the rapid progress in this field. All existing measurements confirm CPT symmetry within their respective uncertainties.…”