Ca+ Ions Solvated in Helium Clusters.
Massimiliano BartolomeiPaul MartiniRicardo Pérez de TudelaTomás González-LezanaMarta I HernándezJosé Campos-MartínezJavier Hernández-RojasJosé BretónPaul ScheierPublished in: Molecules (Basel, Switzerland) (2021)
We present a combined experimental and theoretical investigation on Ca+ ions in helium droplets, HeNCa+. The clusters have been formed in the laboratory by means of electron-impact ionization of Ca-doped helium nanodroplets. Energies and structures of such complexes have been computed using various approaches such as path integral Monte Carlo, diffusion Monte Carlo and basin-hopping methods. The potential energy functions employed in these calculations consist of analytical expressions following an improved Lennard-Jones formula whose parameters are fine-tuned by exploiting ab initio estimations. Ion yields of HeNCa+ -obtained via high-resolution mass spectrometry- generally decrease with N with a more pronounced drop between N=17 and N=25, the computed quantum HeNCa+ evaporation energies resembling this behavior. The analysis of the energies and structures reveals that covering Ca+ with 17 He atoms leads to a cluster with one of the smallest energies per atom. As new atoms are added, they continue to fill the first shell at the expense of reducing its stability, until N=25, which corresponds to the maximum number of atoms in that shell. Behavior of the evaporation energies and radial densities suggests liquid-like cluster structures.
Keyphrases
- monte carlo
- density functional theory
- molecular dynamics
- high resolution mass spectrometry
- quantum dots
- liquid chromatography
- high resolution
- protein kinase
- climate change
- mass spectrometry
- air pollution
- ultra high performance liquid chromatography
- ms ms
- molecular dynamics simulations
- tandem mass spectrometry
- preterm birth
- preterm infants