Anionic microsolvation in helium droplets: OH- (He)N structures from classical and quantum calculations
E Coccia1, F Marinetti, E Bodo
1Department of Chemistry, University of Rome La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy.
The Journal of Chemical Physics
|April 10, 2008
Summary
Quantum calculations reveal that the negatively charged hydroxyl radical (OH-) is surprisingly solvated in helium droplets, forming a liquidlike layer. This contrasts with cationic dopants, highlighting unique quantum effects in anionic solvation.
Area of Science:
- Quantum chemistry
- Atomic and molecular physics
- Condensed matter physics
Background:
- Helium droplets are weakly interacting systems used to study solvation.
- Anionic impurities in helium droplets exhibit different behavior compared to cationic ones.
- Understanding solvation of molecular ions is crucial for cluster science.
Purpose of the Study:
- To investigate the solvation structure and quantum delocalization of the OH- anion in helium droplets.
- To compare the behavior of anionic impurities with previously studied cationic dopants.
- To explore the applicability of classical methods for describing solvent adatoms around anions.
Main Methods:
- Diffusion Monte Carlo (DMC) calculations for N up to 15 helium atoms.
- Genetic algorithm optimization for classical configurations up to N=20.
- Ab initio data and sum-of-potentials scheme for interaction potential.
Main Results:
- Significant spatial delocalization and quantum features of helium adatoms around the OH- anion.
- Classical calculations of solvent locations are of limited use due to quantum effects.
- The polar molecular anion OH- is solvated by a liquidlike layer, similar to pure helium droplets.
Conclusions:
- Anionic impurities like OH- display distinct solvation characteristics in helium droplets compared to cations.
- Quantum effects dominate the spatial distribution of solvent atoms around the anion.
- The solvation of OH- in helium droplets resembles that of pure helium droplets, despite charge repulsion.
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