The structure of the minimum unit of the radical cationic water clusters, the (HO) dimer, has attracted much attention because of its importance for the radiation chemistry of water. Previous spectroscopic studies indicated that the dimers have a proton-transferred structure (HO·OH), though the alternate metastable hemibonded structure (HO·OH) was also predicted based on theoretical calculations. Here, we produce (HO) dimers in superfluid helium nanodroplets and study their infrared spectra in the range of OH stretching vibrations. The observed spectra indicate the coexistence of the two structures in the droplets, supported by density functional theory calculations. This is the first spectroscopic identification of the hemibonded isomer of water radical cation dimers. The observation of the higher-energy isomer reveals efficient kinetic trapping for metastable ionic clusters due to the rapid cooling in helium droplets.
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http://dx.doi.org/10.1021/acs.jpclett.3c02150 | DOI Listing |
J Chem Phys
January 2025
Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
Typical path integral Monte Carlo approaches use the primitive approximation to compute the probability density for a given path. In this work, we develop the pair discrete variable representation (pair-DVR) approach to study molecular rotations. The pair propagator, which was initially introduced to study superfluidity in condensed helium, is naturally well-suited for systems interacting with a pairwise potential.
View Article and Find Full Text PDFNat Commun
January 2025
CNR Nanotec, Institute of Nanotechnology, via Monteroni, 73100, Lecce, Italy.
Macroscopic coherence in quantum fluids allows the observation of interference effects in their wavefunctions, and enables applications such as superconducting quantum interference devices based on Josephson tunneling. The Josephson effect manifests in both fermionic and bosonic systems, and has been well studied in superfluid helium and atomic Bose-Einstein condensates. In exciton-polariton condensates-that offer a path to integrated semiconductor platforms-creating weak links in ring geometries has so far remained challenging.
View Article and Find Full Text PDFJ Chem Phys
December 2024
Departament FQA, Facultat de Física, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain.
We study superfluid helium droplets multiply charged with Na+ or Ca+ ions. When stable, the charges are found to reside in equilibrium close to the droplet surface, thus representing a physical realization of Thomson's model. We find the minimum radius of the helium droplet that can host a given number of ions using a model whose physical ingredients are the solvation energy of the cations, calculated within the helium density functional theory approach, and their mutual Coulomb repulsion energy.
View Article and Find Full Text PDFJ Chem Phys
November 2024
Université Paris-Saclay, Univ Evry, CY Cergy Paris Université, CNRS, LAMBE, Evry-Courcouronnes 91025, France.
The collision of cesium atoms on the surface of helium nanodroplets (HNDs) containing 1000 atoms is described by the ZPAD-mPL approach, a zero-point averaged dynamics (ZPAD) method based on a He-He pseudopotential adjusted to better reproduce the total energy of He1000. Four types of collisional patterns were identified depending on the initial projectile speed v0 and impact parameter b. At the lowest speeds (v0 ≲ 250 m s-1), Cs atoms are softly captured by the HND surface, while at the highest ones (v0 ≳ 500-600 m s-1), Cs atoms can travel through the droplet and move away.
View Article and Find Full Text PDFRep Prog Phys
November 2024
Department of Physics and Astronomy, Aarhus University, 8000 Aarhus, C, Denmark.
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