Near-thermo-neutral electron recombination of titanium oxide ions
Abstract
While the dissociative recombination (DR) of ground-state molecular ions with low-energy free electrons is generally known to be exothermic, it has been predicted to be endothermic for a class of transition-metal oxide ions. To understand this unusual case, the electron recombination of titanium oxide ions (TiO+) with electrons has been experimentally investigated using the Cryogenic Storage Ring. In its low radiation field, the TiO+ ions relax internally to low rotational excitation (≲100 K). Under controlled collision energies down to ∼2 meV within the merged electron and ion beam configuration, fragment imaging has been applied to determine the kinetic energy released to Ti and O neutral reaction products. Detailed analysis of the fragment imaging data considering the reactant and product excitation channels reveals an endothermicity for the TiO+ dissociative electron recombination of (+4 ± 10) meV. This result improves the accuracy of the energy balance by a factor of 7 compared to that found indirectly from hitherto known molecular properties. Conversely, the present endothermicity yields improved dissociation energy values for D0(TiO) = (6.824 ± 0.010) eV and D0(TiO+) = (6.832 ± 0.010) eV. All thermochemistry values were compared to new coupled-cluster calculations and found to be in good agreement. Moreover, absolute rate coefficients for the electron recombination of rotationally relaxed ions have been measured, yielding an upper limit of 1 × 10−7 cm3 s−1 for typical conditions of cold astrophysical media. Strong variation of the DR rate with the TiO+ internal excitation is predicted. Furthermore, potential energy curves for TiO+ and TiO have been calculated using a multi-reference configuration interaction method to constrain quantum-dynamical paths driving the observed TiO+ electron recombination.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 13, 2023
- Source ID
- 10.1063/5.0146365
Entities
People
- Albert A Viggiano
- Andreas Wolf
- Daniel Paul
- Dominique M. Maffucci
- Evangelos Miliordos
- Felix Nuesslein
- Manfred Grieser
- Michael C Heaven
- Naman Jain
- Nicholas S Shuman
- Oldrich Novotny
- Patrick Wilhelm
- Robert Von Hahn
- Shaun G Ard
- Ábel Kálosi
Organizations
- Air Force Office of Scientific Research
- Air Force Research Laboratory
- Auburn University
- Columbia University
- Emory University
- Max Planck Institute for Nuclear Physics
- Max Planck Society
- National Science Foundation