Interaction Of Rare Gas Atoms Research Articles

Theoretical investigation of the weak interactions of rare gas atoms with silver clusters by resonance Raman spectroscopy modeling

AbstractThe interactions of rare gas atoms (Rg = Ar, Kr, and Xe) with small neutral and cationic silver clusters have been investigated by density functional methods and the effect of these weak interactions on the resonance Raman spectra of the complexes has been evaluated. The resonance Raman technique that depends on the properties of ground and excited state, seems deeply sensitive to the weak rare gas–metal cluster interactions, and the use of inert gases has been proven to be an excellent approach to recognize the ability of this technique to detect extremely weak interactions. In this work, for , and complexes the IR, normal and resonance Raman spectra have been calculated and the effect of rare gas–cluster stretching vibration ( ) on the pattern and the relative intensities of different spectra have been investigated. The resonance Raman spectra for the weakly interacted complexes (with the interaction energies less than −2.0 kcal/mol) exhibit the vibration with the detectable intensity that its intensity increases by going from Ag6–Ar to Ag6–Xe complex. Moreover, the resonance Raman spectra (based on the excited state gradient approximation) for high intensity nearly degenerate excited states, proved the effect of accumulation of the excited state charge density on the relative intensity of vibration.

Investigation of the Electronic Excited States of Small Gold Clusters in Rare Gas Matrices: Spin-Orbit Time-Dependent Density Functional Theory Calculation.

The effects of the weak interactions of rare gas atoms on the UV-visible absorption spectra of gold dimer and tetramer clusters are investigated. The time-dependent density functional theory based on the two-component relativistic zeroth-order regular approximation that considered spin-orbit coupling is performed to estimate the absorption spectra of Au2,4-Rgn (Rg = Ne-Xe, and n = 1-6) complexes. Using spin-orbit, including the appropriate functional, shows a close correlation between experiment and our calculations. It is also demonstrated that the weak interactions between rare gas atoms and gold clusters affect the UV-vis spectra of Au2,4 clusters by shifting the electronic transition toward the blue. Moreover, we find that the order of change in peak position, Δν̃, is proportional to the strength of interactions: Δν̃Au2,4-Xe > Δν̃Au2,4-Kr > Δν̃Au2,4-Ar > Δν̃Au2,4-Ne. In addition, comparing the UV-visible spectra of Au2,4-Rgn complexes with those of isolated Au2 and Au4 clusters shows that for Au2,4-Rg2,4,6 complexes in which Rg atoms interacted symmetrically with gold clusters no additional peaks are observed compared to isolated clusters; however, for Au2,4-Rg1,3,5 complexes, extra peaks appear because of the decrease in symmetry.

Product state resolved excitation spectroscopy of He–, Ne–, and Ar–Br2 linear isomers: Experiment and theory

Valence excitation spectra for the linear isomers of He-, Ne-, and Ar-Br2 are reported and compared to a two-dimensional simulation using the currently available potential energy surfaces. Excitation spectra from the ground electronic state to the region of the inner turning point of the Rg-Br2 (B,nu') stretching coordinate are recorded while probing the asymptotic Br2 (B,nu') state. Each spectrum is a broad continuum extending over hundreds of wavenumbers, becoming broader and more blueshifted as the rare gas atom is changed from He to Ne to Ar. In the case of Ne-Br2, the threshold for producing the asymptotic product state reveals the X-state linear isomer bond energy to be 71+/-3 cm(-1). The qualitative agreement between experiment and theory shows that the spectra can be correctly regarded as revealing the one-atom solvent shifts and also provides new insight into the one-atom cage effect on the halogen vibrational relaxation. The measured spectra provide data to test future ab initio potential energy surfaces in the interaction of rare gas atoms with the halogen valence excited state.

Ab initiomolecular-dynamics studies of doped magic clusters and their interaction with atoms

We present results of the atomic and electronic structure of icosahedral ${\mathrm{Al}}_{12}X$ $(X=\mathrm{S}\mathrm{i}$, Ge, and Sn) clusters using the ab initio molecular-dynamics method within the local density functional theory. Substitutional doping of a ${\mathrm{Al}}_{13}$ cluster by a tetravalent atom leads to a substantial gain in energy in all the cases studied. Tin is found to have a lower energy at a vertex site in contrast to the central site for Si and Ge, leading to surface segregation of Sn in these clusters. Also in the case of a ${\mathrm{Al}}_{13}\mathrm{Si}$ cluster, Si occupies the central site of a capped icosahedral structure. These results when interpreted in terms of the interaction of closed shell clusters with atoms leads to a relatively strong interaction of ${\mathrm{Al}}_{12}\mathrm{Si}$ with $\mathrm{Al}$ as compared to the weak interaction of rare gas atoms with other elements.

The interaction of rare gases with transition metal surfaces

The interaction of rare gas atoms with metal surfaces is considerably modified in the presence of occupied Shockley surface states. The anomalous bond strength of Xe on Pd, the decoration of upper step edges on Pt(111), and the different XeXe interaction on Pd and Pt is at least partially accounted for by the influence of surface states. Arguments are provided that surface states also contribute to the anticorrugating effects observed in He scattering on Ni(110) and Cu(110).

Test of interaction potentials for rare gas-halide systems

Ab initio, model and empirical potentials for the interaction of rare gas atoms and halide ions are tested by their ability to reproduce gaseous ion transport data. The ab initio potentials are in poor agreement with the data. The model potentials give good agreement with experiment for some systems, moderate agreement for others, and very poor agreement for Br− in Ar, Kr and Xe. The potentials that were directly determined in 1985 from gaseous ion transport data more closely match those data and newer transport data than do any of the potentials proposed subsequently, with the exception of potentials inferred from zero electron kinetic energy spectroscopy.

Intramolecular bond length dependence of the anisotropic dispersion coefficients for interactions of rare gas atoms with N2, CO, Cl2, HCl and HBr

Ab initio many body perturbation theory is used to calculate the imaginary frequency multipole polarizabilities of N2, Cl2, CO, HCl and HBr as a function of bond length. These are combined with previously calculated dynamic polarizabilities for rare gas atoms to obtain the intramolecular bond length dependence of the anisotropic dispersion and induction coefficients through R -8 for AB-X (AB = N2, Cl2, CO, HCl, HBr and X = He, Ne, Ar, Kr, Xe) interactions.

The representation of van der Waals (vdW) interactions in molecular mechanics force fields: potential form, combination rules, and vdW parameters

This paper explores the premise that insights gained from studying the well-characterized van der Waals (vdW) interactions of rare-gas atoms can be used advantageneoulsy in formulating the representation of vdW nonbonded interactions in molecular mechanics force fields, a subject to which little attention has been givin to date

The interaction of rare gas atoms with metal surfaces: a scattering theory approach

The scattering theory formulation of the helium-metal surface interaction due to Zaremba and Kohn has been generalized to treat the entire rare gas sequence. The atom-surface repulsion is determined in terms of atomic HF T-matrix elements and is combined with a damped van der Waals interaction to produce total physisorption potentials. A systematic comparison is made between these potentials and those calculated in our earlier work based on the pseudopotential method originally developed by Harris and Liebsch. Although both formulations lead to similar trends in the calculated potentials, the latter treatment overestimates the repulsion between the adsorbate and the surface over the entire physisorption region and results in final potentials which are too shallow, particularly for the heavier rare gases. We find that our present results are in good agreement with existing experimental trends for the rare gases on various metals.

Interaction of rare gas atoms with metal surfaces: A pseudopotential approach

Interaction of rare gas atoms with metal surfaces: A pseudopotential approach

Interaction of rare gas atoms with metal surfaces: A pseudopotential approach

The pseudopotential formulation of the helium-metal surface interaction due to Harris and Liebsch has been generalized to treat the heavier rare gases. The atom-surface repulsion is calculated to first-order in the pseudopotential and is combined with a damped van der Waals interaction to produce the total physisorption potential. Reasonable results are obtained for all the rare gases considered, with a systematically increasing potential-well depth through the rare gas sequence. A single surface-atom model is also considered and its limitations discussed.

Molecular-beam spectroscopic studies of intermolecular interactions

The results of molecular-beam electric-resonance studies of weakly bound van der Waals complexes are discussed. The use of spectroscopic constants to investigate intermolecular interactions is critically examined. Potential surfaces for the interaction of rare-gas atoms and hydrogen halides are presented and their accuracy is assessed.

Many-orbital cluster expansion for the exchange-repulsion nonadditivity in the interaction of rare gas atoms. The neon trimer

Nonadditivity of the exchange repulsion for three neon atoms in the equilateral triangle configuration has been calculated in the first-order of the symmetry adapted perturbation theory. The relative nonadditive contribution to the first-order interaction energy has been found to be about twice as small as in the helium trimer. The many-orbital cluster partition of the exchange nonadditivity has been derived. It has been found that in the region of the van der Waals minimum about 95% of the exchange nonadditivity originates from the interaction of the L-shell electrons only. The five-orbital terms as well as terms of an order-higher than S3 have been found to be negligible. Approximate formulae for evaluation of the exchange repulsion nonadditivity has been proposed and discussed.

The interaction of rare gas atoms with graphitized carbon black

The interaction of rare gas atoms with graphitized carbon black

The interaction of rare gas atoms with graphite surfaces. II. Adatom–adatom potentials

The Gordon–Kim local density method is applied to the calculation of the interaction energy of pairs of neon, argon, and krypton atoms adsorbed on the basal plane of graphite. At the adatom–surface equilibrium separation, the adatom–adatom interaction potentials are found to be from 12% to 20% more repulsive than the gas phase counterparts. At much smaller adatom–surface separations, the adatom–adatom effective potential well depth is only 3% of the gas phase well depth. It is found that the nonadditive contributions to the interaction energy are more important for the smaller rare gas adatoms than for the larger ones. This trend is observed experimentally. It is concluded that rare gas films on graphite are too mobile to be in registry with the substrate.

Nonadditive three-body interactions of rare-gas atoms. II. Intermediate and large distances

Nonadditive three-body interactions of rare-gas atoms. II. Intermediate and large distances

The interaction of rare gas atoms with graphite surfaces. I. Single adatom energies

The Gordon−Kim local density method is applied to the calculation of the interaction energy of helium, neon, argon, and krypton with the basal plane of graphite. In all cases, the binding site is found to be above the center of a hexagon, but the barrier to migration to other sites is less than 50 cal/mole. Comparisons are made with other studies on these systems, and the role of non−two−body additive effects is discussed.

Morse-6 Hybrid Potentials for Pair Interactions of Rare Gas Atoms

Hybrid pair potential functions are constructed from three parts: (1) a short-range exponential repulsion of the form A exp (−λr), obtained from either Self-Consistent-Field or Thomas-Fermi-Dirac calculations; (2) a long-range dipole-dipole dispersion attraction −C6r−6 where the C6 coefficients are obtained from highly accurate semiempirical estimates; (3) a Morse potential A exp (−λr) −B exp (−λr/2), whose B parameter is found by fitting experimental second virial coefficients, and which is used to connect the long- and short-range segments. The bowls of the resulting potentials depend most perceptibly on the nature of the repulsive limb from which they are constructed. Potentials are constructed which describe He–Ne, He–Ar, Ne–Ne, Ne–Ar, Ar–Ar, Ar–Kr, Kr–Kr, and Xe–Xe interactions. The vibrational energy eigenvalues and spectroscopic constants are determined for these potentials. Comparison with the available experimental spectroscopic data and low energy molecular beam results is presented. Our most likely Morse-6 hybrids for ArAr, for example, give good agreement with molecular beam measurements, with the Tanaka and Yoshino spectroscopic measurements, and with the very flexible Barker-Pompe-Bobetic empirical potential.

The Interaction of Rare Gas Atoms with Surfaces

The apparent volumes of vessels containing high surface area powders have been measured with rare gases and analyzed. The interaction energies and distances of closest approach have been evaluated. A new method for the estimation of surface area is presented.