Antiprotonic helium atomcules
2012 (English)In: From Quantum Chemistry To Astrophysics: A Tribute To Pierre Valiron, EDP Sciences, 2012, 03002- p.Conference paper (Refereed)
About 3% of antiprotons (p̄) stopped in helium are long-lived with microsecond lifetimes, against picoseconds in all other materials. This unusual longevity has been ascribed to the trapping of p̄ on metastable bound states in p̄He+ helium atom-molecules thus named atomcules. Apart from their unique dual structure investigated by laser spec-troscopy - a near-circular quasi-classical Rydberg atom with l ∼ n - 1 ∼ 37 or a special diatomic molecule with a negatively charged p̄ nucleus in high rotational state with J = l - the chemical physics aspects of their interaction with other atoms or molecules constitute an interesting topic for molecular physics. While atomcules may resist to million collisions in helium, molecular contaminants such as H2 are likely to destroy them in a single one, down to very low temperatures. In the Born-Oppenheimer framework, we interpret the molecular interaction obtained by ab initio quantum chemical calculations in terms of classical reactive channels, with activation barriers accounting for the experiments carried out in He and H2. From classical trajectory Monte Carlo simulations, we show that the thermalization stage strongly quenches initial populations, thus reduced to a recovered 3 % trapping fraction. This work illustrates the pertinence of chemical physics concepts to the study of exotic processes involving antimatter. New insights into the physico-chemistry of cold interstellar radicals are anticipated.
Place, publisher, year, edition, pages
EDP Sciences, 2012. 03002- p.
, EPJ Web of Conferences, ISSN 2101-6275 ; 34
Other Chemistry Topics Other Physics Topics
IdentifiersURN: urn:nbn:se:kth:diva-129806DOI: 10.1051/epjconf/20123403002ISI: 000326392400008ScopusID: 2-s2.0-84883063529OAI: oai:DiVA.org:kth-129806DiVA: diva2:653932
From Quantum Chemistry to Astrophysics: A Tribute to Pierre Valiron, QCA 2010; Grenoble; France; 5 October 2010 through 5 October 2010
QC 201310072013-10-072013-10-042015-11-30Bibliographically approved