ERC FUNDED PROJECTS

Antihydrogen is the simplest atom consisting entirely of antimatter. Since its counterpart hydrogen is one of the best studied atoms in physics, a comparison of antihydrogen and hydrogen offers one of the most sensitive tests of CPT symmetry. CPT, the successive application of charge conjugation, parity and time reversal transformation is a fundamental symmetry conserved in the standard model (SM) of particle physics as a consequence of a mathematical theorem. These conditions for this theorem to be fulfilled are not valid any more in extensions of the SM like string theory or quantum gravity. Furthermore, even a tiny violation of CPT symmetry at the time of the big bang could be a cause of the observed antimatter absence in the universe. Thus the observation of CPT violation might offer a first indication for the validity of string theory, and would have important cosmological consequences. This project proposes to measure the ground state hyperfine (HFS) splitting of antihydrogen (HBAR), which is known in hydrogen with relative precision of 10^–12. The experimental method pursued within the ASACUSA collaboration at CERN-AD consists in the formation of an antihydrogen beam and a measurement using a spin-flip cavity and a sextupole magnet as spin analyser like it was done initially for hydrogen. A major milestone was achieved in 2010 when antihydrogen was first synthesized by ASACUSA. In the first phase of this proposal, an antihydrogen beam will be produced and the HBAR-HFS will be measured to a precision of around 10^–7 using a single microwave cavity. In a second phase, the Ramsey method of separated oscillatory fields will be used to increase the precision further. In parallel methods will be developed towards trapping and laser cooling the antihydrogen atoms. Letting the cooled antihydrogen escape in a field free region and perform microwave spectroscopy offers the ultimate precision achievable to measure the HBAR-HFS and one of the most sensitive tests of CPT.

2 599 900 €

Start date: 2012-03-01, End date: 2017-02-28

Terahertz frequencies match the vibrations between large functional groups in molecular networks from macromolecules, nano-droplets to proteins. If we are able to measure these oscillations we can decipher the structure and the long-range interactions in large molecular systems. This yields a precise fingerprint of the molecule that is highly useful for sensitive trace analysis. However, despite of a lot of research in the field, high precision spectroscopy in the former terahertz gap for isolated large molecular networks has not been developed yet. In this project I will develop the necessary tools to measure terahertz transition frequencies in large, mass-selected molecular systems with high resolution. For this purpose a cryogenic radiofrequency ion trap will be coupled to a terahertz resonator cavity. This will allow excitation of a dilute sample of molecular ions in well-defined internal quantum states with single-frequency terahertz radiation. My vision is to achieve high spectral resolution and single-ion sensitivity for almost arbitrarily large molecular systems in the terahertz regime which will initiate a new field for molecular spectroscopy. To explore the potential of the newly-developed methods, I propose to study molecular networks of fundamental importance in chemistry, biology and astronomy. Vibration-tunneling dynamics will be studied in water cluster ions. Torsional motion of biological chromophores and its role in the quenching of the fluorescent state will be investigated. And the spectral signatures of molecules that are promising candidates for detection in the interstellar medium will be determined.

1 471 200 €

Start date: 2012-01-01, End date: 2016-12-31

"The field of attosecond science is now entering the second decade of its existence, with good prospects for breakthroughs in a number of areas. We want to take the next step in this development: from mastering the generation and control of attosecond pulses to breaking new marks starting with the simplest systems, atoms. The aim of the present application is to advance the emerging new research field “Ultrafast Atomic Physics”, where one- or two-electron wave packets are created by absorption of attosecond pulse(s) and analyzed or controlled by another short pulse. Our project can be divided into three parts: 1. Interferometric measurements using tunable attosecond pulses How long time does it take for an electron to escape its potential? We will measure photoemission time delays for several atomic systems, using a tunable attosecond pulse source. This type of measurements will be extended to multiple ionization and excitation processes, using coincidence measurements to disentangle the different channels and infrared ionization for analysis. 2. XUV pump/XUV probe experiments using intense attosecond pulses How long does it take for an atom to become an ion once a hole has been created? Using intense attosecond pulses and the possibility to do XUV pump/ XUV probe experiments, we will study the transition between nonsequential double ionization, where the photons are absorbed simultaneously and all electrons emitted at the same time and sequential ionization where electrons are emitted one at a time. 3. ""Complete"" attosecond experiments using high-repetition rate attosecond pulses We foresee a paradigm shift in attosecond science with the new high repetition rate systems based on optical parametric chirped pulse amplification which are coming to age. We want to combine coincidence measurement with angular detection, allowing us to characterize (two-particle) electronic wave packets both in time and in momentum and to study their quantum-mechanical properties."

2 047 000 €

Start date: 2014-03-01, End date: 2019-02-28