A combined experimental and theoretical investigation of Cs+ ions solvated in HeN clusters

Abstract

Solvation of Cs + ions inside helium droplets has been investigated both experimentally and theoretically. On the one hand, mass spectra of doped helium clusters ionized with a crossed electron beam, HeNCs + , have been recorded for sizes up to N = 60. The analysis of the ratio between the observed peaks for each size N reveals evidences of the closure of the first solvation shell when 17 He atoms surround the alkali ion. On the other hand, we have obtained energies and geometrical structures of the title clusters by means of basin-hopping, diffusion Monte Carlo (DMC), and path integral Monte Carlo (PIMC) methods. The analytical He-Cs + interaction potential employed in our calculations is represented by the improved Lennard-Jones expression optimized on high level ab initio energies. The weakness of the existing interaction between helium and Cs + in comparison with some other alkali ions such as Li + is found to play a crucial role. Our theoretical findings confirm that the first solvation layer is completed at N = 17 and both evaporation and second difference energies obtained with the PIMC calculation seem to reproduce a feature observed at N = 12 for the experimental ion abundance. The analysis of the DMC probability distributions reveals the important contribution from the icosahedral structure to the overall configuration for He 12 Cs + .

Complexes of Alkali Metal Cations and Molecular Hydrogen: Potential Energy Surfaces and Bound States

“…requires accurate yet simple expressions for the total PES. 26,27 The paper is organized as follows. In Section 2, the theoretical model is presented,…”

Considerable matrix shift in the electronic transitions of helium-solvated cesium dimer cation Cs2He+n

“…The first solvation layer is particularly strongly bound, and its closure is typically reflected as a clear intensity drop of the ion series (with M + the alkali metal ion) in mass spectra. 48 , 50 – 52 Path integral or basin-hopping methods reproduce the experiments very well. 44 , 45 It was also shown previously that helium adsorption might lead to appreciable spectral shifts.…”

Ca+ Ions Solvated in Helium Clusters

“…In addition, HNDs constitute a powerful spectroscopic matrix to study a variety of atomic and molecular species [11]. In particular, many studies have addressed the solvation of alkali ions using this technique [10,[12][13][14][15][16][17]. For alkali-earth ions, although various theoretical simulations of their solvation in He have been reported [5,6,[18][19][20][21][22], experimental studies are very scarce [23].…”

“…In this paper, we present a combined experimental and theoretical study on He N Ca + clusters, following a similar spirit of previous investigations on either helium or molecular hydrogen complexes doped with Li + or Cs + ions [16,17,24]. Measurements of ion yield abundances after ionization of doped HNDs are analyzed along with theoretical calculations performed with PIMC, diffusion Monte Carlo (DMC) and basin-hopping (BH) methods for both energies and structures of He N Ca + clusters.…”