New insights in the low energy electron-driven reactivity of molecular cations
J´anos Zsolt Mezei1,2∗, Jeoffrey Boffelli2, Fr´ed´eric Gauchet2, Andrea Orb´an1, Kalyan Chakrabarti3, Dahbia Talbi4 and Ioan F Schneider2,5†
1 Institute for Nuclear Research (ATOMKI), Debrecen, H-4001, Hungary
2 LOMC, University Le Havre Normandy, Le Havre, 76600, France
3Scottish Church College, University of Calcutta, Calcutta, 700006, India
4 LUPM, Montpellier University, Montpellier, 34095, France
5LAC, University Paris-Saclay, Orsay, 91405, France
Synopsis The major mechanisms governing the fragmentation dynamics induced by the reactive collisions of electrons with molecular cations will be illustrated in the case of the positive molecular hydrogen ions and several diatomic and triatomic hydrides.
Electron-impact dissociative recombination, ro-vibrational (de)excitation and dissociative ex- citation of hydride cations
AB++e−→AB∗,∗∗→
A+B AB0++e− A+B++e−
, (1)
are in the heart of molecular reactivity in the cold ionized media [1], being major charged particles destruction reactions and producing often atomic species in metastable states, inaccessible through optical excitations. They involve super-excited molecular states undergoing predissociation and autoionization, having thus strong resonant char- acter. Consequently, they are subject to beyond- Born-Oppenheimer theoretical approximations, and often require rather quasi-diabatic than adi- abatic representations of the molecular states. In addition, they involve particularly sophisticated methods for modelling the collisional dynamics, able to manage the superposition of many con- tinua and infinite series of Rydberg states.
We use the Multichannel Quantum Defect Theory [2], capable to account the strong mix- ing between ionization and dissociative channels, open - direct mechanism - and closed - indi- rect mechanism, via capture into prominent Ry-
dberg resonances [3,4] correlating to the ground and excited ionic states, and the rotational ef- fects. These features will be illustrated for several cations of high astrophysical and cold plasma physical relevance such as SH+ [5] and CH+ [4, 6, 7], comparisons with other existing theoretical and experimental results being per- formed.
Advancement in the theoretical treatment - as the effect of the energy-dependence of the quantum defect on vibronic interactions for the benchmark cation H+2, the spin-orbit coupling for HCl+, the isotopic effects for polyatomic systems like N2H+, etc. - will be presented.
Research supported by the Normandy region, CNRS-PCMI, ANR Labex EMC3 and NKFIH- OTKA.
References
[1] I. F. Schneider, O. Dulieu, and J. Robert (editors) 2015 Eur. Phys. J. Web of Conf.84
[2] Ch. Jungen (editor), 1996Molecular Applications of Quantum Defect Theory, (IoP Publish. Bristol) [3] I. F. Schneideret al1991J. Phys. B24, L289 [4] Mezei J Zs et al 2019 ACS Earth and Space
Chen,3 2376
[5] D. O. Kashinski et al 2017 J. Chem. Phys. 146, 204109
[6] A. Faureet al2017MNRAS469, 612
[7] K. Chakrabartiet al2018J. Phys. B51, 104002
∗E-mail: mezei.zsolt@atomki.hu
†E-mail: ioan.schneider@univ-lehavre.fr
