Polar molecules engaged in pendular states captured by molecular-beam scattering experiments

Abstract

We demonstrate that when two polar molecules as those of water, ammonia, and hydrogen sulfide encounter each other at a distance much larger than their dimensions they engage a synchronous motion that promotes the transformation of free rotations into coupled pendular states. This discovery has been prompted by high-resolution molecular beam scattering experiments presented here, addressed to the measure of the total integral cross section changes as a consequence of molecular rotation couplings. The experimental observations and the theoretical treatment developed to shed light on the details of the phenomenon suggest that the interplay among free rotations and pendular states depends on the relative velocity, on the rotational levels, and on the dipole moments of the interacting molecules. The features of this intriguing phenomenon may be crucial for the interpretation and the control of basic chemical and biological processes.

The Selective Role of Long‐Range Forces in the Stereodynamics of Ion–Molecule Reactions: The He++Methyl Formate Case From Guided‐Ion‐Beam Experiments

“…Left: at large distances (or highc ollision energies)t he MF molecule freely rotatesaround either of the two main axes of inertia (only rotation around one axis is shownfor clarity);Right:a ts horter distances MF is trappedi nits preferential orientation,i nwhich only bendingv ibrations of the collision complexa re possible. We note that for less anisotropic systems, the lifetime of such naturalmolecular polarisationi sw ithin the timescale of picosecond and/or sub-picosecond, [85,86] comparabletoo rs horter than the presentc ollision time,e speciallyatl ow collision energies. ChemPhysChem 2018, 19,51-59 www.chemphyschem.org ciative and non-dissociativec harge-transfer processes, and the results have been interpreted as being due to system-specific details of the surfacec rossings determined by the long-range anisotropic interactions.…”

Stereoselectivity in Autoionization Reactions of Hydrogenated Molecules by Metastable Noble Gas Atoms: The Role of Electronic Couplings

“…The obtained angular cones have been indicated as “effective” since they are averaged over the probed energy range. In addition, “natural” molecular orientation effects, operative during the collision of polar molecules (as the ones here investigated), induced by electric field gradients in the strongly anisotropic intermolecular potential, should reduce the acceptance angular cones around the direction of more attractive configurations and this effect should increase with the decrease of the collision energy, especially in the subthermal range . It is interesting to note that such “natural” electric field gradients can often be stronger than those artificially generated by external brute force methods …”

Chirality of weakly bound complexes: The potential energy surfaces for the hydrogen-peroxide−noble-gas interactions

“…36,37,39,42 In these cases and in general, extensions to more complex molecules may require additions to the van der Waals interactions, such as electrostatic and charge-transfer contributions.…”

“…Complexes with noble gases (Ng) are especially relevant as reference systems for isolating the importance of the vdW plus induction contributions, permitting to attention on the role of the Ng polarizability: indeed since along the Ng series this key quantity spans a range covering that of the molecules most relevant in general, and in particular under focus in our current research (H 2 , O 2 , H 2 O, NH 3 ). [35][36][37][38][39][40][41][42] Our specific objective is to develop a theoretical framework to study the dynamics of chiral molecules interacting by non-covalent forces with other atoms or molecules, see, e.g., Refs. 18 and 43.…”

“…45,46 Such method, based on the analysis of an ample phenomenology of systems including closed and open shell atoms, positive and negative ions, and simple molecules, provided the guidelines of this and of previous investigations. [35][36][37][38][39][40][41][42]44 The analysis of the PES sheds light on several interesting features of these systems: the role that the enantiomeric forms and the symmetry of the H 2 O 2 molecule play on the resulting chiral geometries; the presence of a local minimum geometry besides the two global ones; and finally, the lower radial limits for the correct representation of the ab initio energies that indicates the region where charge transfer effects begin to be important: these limits depend on the systems, and are currently being investigated. In Sec.…”