Rostock 2019 – scientific programme
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MO: Fachverband Molekülphysik
MO 15: Cold Molecules (joint session MO/A)
MO 15.8: Talk
Wednesday, March 13, 2019, 15:45–16:00, S HS 002 Biologie
Manipulation of molecular hydrogen on a chip to study cold collisions with a merged beam apparatus — •Katharina Höveler1, Johannes Deiglmayr2, Pitt Allmendinger1, Josef Agner1, Hansjürg Schmutz1, and Frédéric Merkt1 — 1Laboratorium für Physikalische Chemie, ETH Zürich, 8093 Zurich, Switzerland — 2Felix-Bloch Institut, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
The exothermic, barrierless H2++H2 →H3++H reaction has been studied in the collision-energy range Ecoll / kb = 0.3−50 K. To reach such low collision energies, we use a merged-beam approach and substitute the H2+ reactants by the ionic cores of H2 molecules in high-n Rydberg-Stark states. The Rydberg electron does not influence the reaction but shields the ion from heating by space-charge effects and stray electric fields. A curved surface-electrode device is used to deflect a supersonic beam of H2 molecules excited to high-n Rydberg-Stark states and to merge it with a supersonic beam containing ground-state H2 molecules. The collision energy is tuned by varying the temperature of the valve generating the H2 ground-state beam for selected velocities of the deflected H2 beam. The reaction cross section is found to follow the classical Langevin capture model down to Ecoll / kb=5 K. At lower temperatures, a deviation is observed and attributed to ion-quadrupole long-range interactions. Investigation of the reaction H2++D2 enables us to distinguish between charge transfer, D atom transfer and H+ ion transfer and to determine the ratio of the two competing reaction channels leading to the product ions H2D+ and D2H+.