Antihydrogen atoms are routinely formed at CERN in a broad range of Rydberg states. Ground-state antiatoms, those useful for precision measurements, are eventually produced through spontaneous decay. However given the long lifetime of Rydberg states the number of ground-state antihydrogen atoms usable is small, in particular for experiments relying on the production of a beam of antihydrogen atoms. Therefore, it is of high interest to efficiently stimulate the decay in order to retain a higher fraction of ground-state atoms for measurements. We propose a method that optimally mixes the high angular momentum states with low ones enabling us to stimulate, using a broadband frequency laser, the deexcitation toward low-lying states, which then spontaneously decay to the ground state. We evaluate the method in realistic antihydrogen experimental conditions. For instance, starting with an initial distribution of atoms within the
n=20−−30 manifolds, as formed through the charge exchange mechanism, we show that more than 80% of antihydrogen atoms will be deexcited to the ground state within 100 ns using a laser producing 2 J at 828 nm.
Antihydrogen atoms are routinely formed at the Antiproton Decelerator at CERN in a wide range of Rydberg states. To perform precision measurements, experiments rely on ground-state antimatter atoms which are currently obtained only after spontaneous decay. In order to enhance the number of atoms in ground state, we propose and assess the efficiency of different methods to stimulate their decay. First, we investigate the use of THz radiation to simultaneously couple all
n-manifolds down to a low-lying one with sufficiently fast spontaneous emission toward ground state. We further study a deexcitation scheme relying on state mixing via microwave and/or THz light and a coupled (visible) deexcitation laser. We obtain close to unity ground-state fractions within a few tens of $\ensuremath{\mu}\mathrm{s}$ for a population initiated in the
n=30 manifold. Finally, we study how the production of antihydrogen atoms via stimulated radiative recombination can favorably change the initial distribution of states and improve the overall number of ground-state atoms when combined with stimulated deexcitation.
High-precision hydrogen spectroscopy is an active field which helps to determine the Rydberg constant and proton charge radius, tests bound-state QED, and can search for Beyond Standard Model (BSM) Physics. Additionally, with recent demonstrations of anti-hydrogen trapping and spectroscopy, a new line of investigation is possible whereby hydrogen can be compared to its antimatter counterpart. The next generation of precision hydrogen spectroscopy will likely require additional motional control of the atomic sample - similar to what is possible with heavier elements. Unfortunately, laser cooling - one of the cornerstones of modern precision atomic physics - is difficult in hydrogen due to the vacuum ultraviolet radiation required. Here, we sidestep the challenges inherent in laser cooling and demonstrate a technique whereby we load metastable atoms from a cryogenic beam into a moving optical lattice, decelerate the lattice, and observe a commensurate deceleration of the atoms. Since the optical lattice is governed by standard optoelectronics, this technique represents a robust platform for the motional control of hydrogen. Our technique could enable greater precision in hydrogen spectroscopy and be transferred to exotic simple atoms such as antihydrogen.
Performing measurements of the properties of antihydrogen, the bound state of an antiproton and a positron, and comparing the results with those for ordinary hydrogen, has long been seen as a route to test some of the fundamental principles of physics. There has been much experimental progress in this direction in recent years, and antihydrogen is now routinely created and trapped and a range of exciting measurements probing the foundations of modern physics are planned or underway. In this contribution we review the techniques developed to facilitate the capture and manipulation of positrons and antiprotons, along with procedures to bring them together to create antihydrogen. Once formed, the antihydrogen has been detected by its destruction via annihilation or field ionization, and aspects of the methodologies involved are summarized. Magnetic minimum neutral atom traps have been employed to allow some of the antihydrogen created to be held for considerable periods. We describe such devices, and their implementation, along with the cusp magnetic trap used to produce the first evidence for a low-energy beam of antihydrogen. The experiments performed to date on antihydrogen are discussed, including the first observation of a resonant quantum transition and the analyses that have yielded a limit on the electrical neutrality of the anti-atom and placed crude bounds on its gravitational behaviour. Our review concludes with an outlook, including the new ELENA extension to the antiproton decelerator facility at CERN, together with summaries of how we envisage the major threads of antihydrogen physics will progress in the coming years.
The dynamics of (de)excitation between highly excited Rydberg states (
15<n<60 of Rb) in a magnetic field of 0.85 $\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ is studied with far-infrared pulses (90--110 and $50\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{m}$) originating from a free electron laser. We measured the excitation spectrum to states around
n=40 from a deeper bound state near
n=25. Moreover, starting from a highly excited state
(30<n<60) below and in the
n-mixing regime we investigated the efficiency of the deexcitation channel vs the ionization channel. We measured deexcitation efficiencies well above 50% for some of the states. However, starting deep in the
n-mixing regime the deexcitation efficiency is less than 10%. The measurements were in good agreement with fully quantum mechanical calculations. Calculations for deexcitation of
n=35 states in H found the largest amount of deexcitation for
m=0 and almost none for
m=20. In recent experiments at CERN, antihydrogen is produced in high
n states in a strong magnetic field with a wide distribution of
m. Our measurements and calculations suggest that deexcitation stimulated by infrared photons is not an efficient method for accelerating cascade to the ground state.