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New experimental methods for trapping cold molecular hydrogen

Project description

Innovative approach overcomes barriers to trapping molecular hydrogen

Consisting of just two protons and two electrons, molecular hydrogen is the simplest molecule found in nature. Its properties can be very accurately calculated from quantum theory laws, but the molecule is difficult to measure experimentally owing to its very weak interactions with electromagnetic fields. In a first, the ERC-funded H2TRAP project will seek to trap molecular hydrogen by using superconducting magnetic traps and ultrahigh-power optical dipole traps. The use of cold and trapped hydrogen samples will allow hydrogen properties to be measured with a higher degree of precision, by at least two orders of magnitude, than previous research efforts.


Due to its simplicity, H2 constitutes a perfect tool for testing fundamental physics: testing quantum electrodynamics, determining fundamental constants, or searching for new physics beyond the Standard Model. H2 has a huge advantage over the other simple calculable systems (such as H, He, or HD+) of having a set of a few hundred ultralong living rovibrational states, which implies the ultimate limit for testing fundamental physics with H2 at a relative accuracy level of 10^-24. The present experiments are far from exploring this huge potential. The main reason for this is that H2 in its ground electronic state extremely weakly interacts with electric and magnetic fields; hence, H2 is not amenable to standard techniques of molecule slowing, cooling, and trapping. In this project, we propose a completely new approach for H2 spectroscopy. For the first time, we will trap a cold sample of H2. We will consider two approaches: superconducting magnetic trap and ultrahigh-power optical dipole trap (with trap depths of the order of 1 mK). T = 5 K will be achieved with a standard refrigeration technique, and the trap will be filled in situ with the 5 K thermal distribution of the H2 sample. Presently, there is no technology available to cool down the H2 gas sample from 5 K to 1 mK; hence, the only option is to directly capture the coldest fraction. The majority of the molecules that initially fill the trap zone will be lost. However, the high initial H2 density will allow us to trap up to 600 000 molecules. We will do infrared-ultraviolet double resonance H2 spectroscopy referenced to the optical frequency comb and primary frequency standard. The ability to do spectroscopy using a cold and trapped sample will eliminate the sources of uncertainty that have limited previous best approaches and will allow us to improve the accuracy by at least two orders of magnitude. The H2 traps will open up a new way for further long-term progress in the metrology of H2 rovibrational lines.

Host institution

Net EU contribution
€ 1 923 238,75
87100 Torun

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Makroregion północny Kujawsko-pomorskie Bydgosko-toruński
Activity type
Higher or Secondary Education Establishments
Total cost
€ 1 923 239,00

Beneficiaries (1)