Cluster size determination from diffractive He atom scattering

Abstract

In a crossed molecular beam arrangement helium atoms are scattered from argon clusters which are produced in an averaged size range of n̄=6 to n̄=90 by adiabatic expansion through sonic and conical nozzles. The diffraction oscillations in the total differential cross section are used to derive information on the size distribution of the clusters by comparison with quantum mechanical calculations based on a model potential. In the size range covered by the measurements, the average cluster size is given by n̄=38.4(Γ*/1000)1.64, where Γ* is the scaling parameter of the source conditions introduced by Hagena [Z. Phys. D 4, 291 (1987)]. The results are in agreement with recent measurements of corrected mass spectra but disagree with the results obtained from electron diffraction. General relations are recommended which connect the scaling parameter with the averaged size.

Character of tightly bound excitons in small argon clusters: Insights from size-dependent energy shifts

“…At a nozzle temperature of 30 K and a stagnation pressure of 200 mbar the average cluster size was determined as N ϭ7500 using well-known scaling laws. 13,14 The width ͓full width at half maximum ͑FWHM͔͒ ⌬N of the size distribution is approximately N . The cluster beam intersects Ar atoms from a cross-jet on a length scale of 10 mm.…”

Ionization of Water Clusters Mediated by Exciton Energy Transfer from Argon Clusters

“…21 For a 50 µm nozzle, with an expansion of 7 bar of Ar, an average cluster size distribution of 20 was reported. At room temperature, the vapour pressure of water is around 20 torr, the beam is composed of 99.6% Ar under our conditions, and thus we believe that the average Ar cluster distribution is also around 20 for the work reported here.…”

“…Very recently an FTIR experiment on water clusters generated under conditions very similar to ours (less than 1% of water seeded in argon with high backing pressure) suggest that small water clusters (n=2-5) were completely solvated by argon clusters composed of between [17][18][19][20][21][22] atoms. 33 This was based on comparison of the vibrational spectrum with ab-initio calculations.…”

Atom scattering from disordered surfaces in the sudden approximation: double collisions effects and quantum liquids

“…It should be noted that it is inconceivable at this point to imagine an experiment which is capable of resolving the details of the energy transfer at the level of surface atoms in a liquid, which is thermalized very quickly. However, such experiments may become possible in the future (indeed, efforts are underway in the context of atomic Ar clusters [39]) so that a formalism capable of describing them is desirable. V and the SCF potentials are not independent; assuming that the influence of the He particle on the surface is small and localized, it should be sufficient to evaluate V at r = 0, thus avoiding the need to find ψ in order to calculate the SCF potentials:…”