Merged-Beams Study of the Reaction of Cold <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>HD</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> with C Atoms Reveals a Pronounced Intramolecular Kinetic Isotope Effect
Florian Grussie, Lukas Berger, M. Grieser, Ábel Kálosi, Damian Müll, O. Novotný, Aigars Znotins, F. Dayou, Xavier Urbain, H. Kreckel
Abstract
We present a merged-beams study of reactions between HD^{+} ions, stored in the Cryogenic Storage Ring (CSR), and laser-produced ground-term C atoms. The molecular ions are stored for up to 20 s in the extreme vacuum of the CSR, where they have time to relax radiatively until they reach their vibrational ground state (within 0.5 s of storage) and rotational states with J≤3 (after 5 s). We combine our experimental studies with quasiclassical trajectory calculations based on two reactive potential energy surfaces. In contrast to previous studies with internally excited H_{2}^{+} and D_{2}^{+} ions, our results reveal a pronounced isotope effect, favoring the production of CH^{+} over CD^{+} across all collision energies, and a significant increase in the absolute rate coefficient of the reaction. Our experimental results agree well with our theoretical calculations for vibrationally relaxed HD^{+} ions in their lowest rotational states.