PSI2 Program DYMCOM
Specific Cases
A short list of specific examples follows.
1. Kelvin to sub-mK chemistry
The challenges between experiments and theory are numerous :
- The CERISES and other similar experiments at FELIX.
- Low-T jets, traps, (including mixed neutral-ion traps) and storage rings present many experimental challenges to be met
- Identical particles low-T chemistry. XHn+, Hn+ vs. Rbn+ . Roles of electronic, nuclear spin, and atomic weight. Experiments and astro applications. Bose-Einstein condensation of alkaline molecules. Deuteration and spin scrambling through exchange reactions. Scaling of Zero-point energy.
- Typical ions or ion molecule reactions of interest and amenable to experiments are, in the Kelvin regime:
He-H3+ and H2-FeO+ ; Binding energy of NH+ (photo dissociation);
Reaction of N+ + H2 and isotope variants.
Radiative association C+ + H, H+ + H2, H3+ + He, Reactions of ions with slow H-atoms - High precision long-range PES, including PES for open shell interacting molecules.
- Reaction mediated by tunnelling. Several prominent examples in astrophysics (H + CO). Compound difficulty: N+H2 —> NH2 + hv (spin-orbit+tunneling). Relevance of very minor rates, like forbidden inter-system crossings.
2. Detachment and recombination. Non Born-Oppenheimer effects are key, as well as proper inclusion of various Rydberg channels in incoming and/or outgoing channels.
- Low-T recombination e- + M+ —> M + hv / A +B / A’ + B’ : Rates , branching ratios. Experiments (traps, ion storage ring) and observational cases, in plasma and astrophysics.
- Dissociative detachment, with similar importance of branching ratios: M- + e- —> M + 2e- / A+B+2e- . M- + X —> A + B + X + e-. Experiments in traps, some astrophysical observations
3. Reactivity
Interesting (and challenging) are reactions involving radicals, all the more if activation energy is absent, but with a submerged barrier. These reactions dominate chemistry at low enough temperatures: (i) Compute reliably and economically such common landscapes (ii) Investigate the importance of roaming type mechanisms at low-T near threshold, in particular the existence, nature and manifestations of quantum roaming.