@article{Zhelyazkova_2022, title={The Effect of the Molecular Dipole and Quadrupole moments on Ion-Molecule Reaction Rates near 0 K }, volume={76}, url={https://www.chimia.ch/chimia/article/view/2022_316}, DOI={10.2533/chimia.2022.316}, abstractNote={<p>We review the results of our recent experimental and theoretical studies of gas-phase ion-molecule reactions involving the He<sup>+ </sup>ion at low collision energies (<em>E<sub>coll</sub></em>), in the k<sub>B</sub>⋅(0 – 40) K range. To avoid heating of the ions by stray electric fields, the reactions are studied within the orbit of a Rydberg electron. We reach collision energies down to ~0 K by employing a merged-beam setup. In the case of a molecule with a dipole moment (e.g., ammonia), we observe a strong enhancement of the measured reaction yield with decreasing <em>E<sub>coll</sub></em>. This enhancement is attributed to rotational states which experience linear negative Stark shifts in the electric field of the ion. When the molecule has no dipole moment but a negative quadrupole moment (e.g., N<sub>2</sub>), we observe a suppression of the total reaction yield at the lowest collision energy. Our results are interpreted with the aid of an adiabatic-channel model.</p>}, number={4}, journal={CHIMIA}, author={Zhelyazkova, Valentina}, year={2022}, month={Apr.}, pages={316–321} }