Noble-Gas Nanoclusters with Fivefold Symmetry Stabilized in Superfluid Helium

Abstract

Macroscopic samples (volume approximately cm(3), atomic density approximately 10(19) -10(20) cm(-3)) of noble-gas nanoclusters (size approximately 5-6 nm) were produced in superfluid helium by an impurity-helium gas injection technique. X-ray diffraction measurements show that the samples consist of weakly interacting nanoclusters with fivefold symmetry, such as icosahedra and decahedra. These results open new opportunities for fundamental research of nanoclusters of noble gases and other materials in well-controlled environments using experimental techniques requiring bulk samples.

Atomic and molecular defects in solid 4He

“…The structure of impurity-helium solids formed by Ne, Kr, N 2 , and D 2 impurities, as well as by a D 2 -Ne mixture in liquid He was investigated in a series of X-ray diffraction experiments [232][233][234]237,242,243]. The observed diffraction patterns consist of overlapping peaks that are characteristic for liquid He and for impurity crystals with a fcc structure.…”

Optical spectroscopy and current detection during warm-up and destruction of impurity–helium condensates

“…The spectral changes observed during the destructions of IHC samples confirm the multishell structure of impurity nanoclusters which form IHCs. The cluster growth occurs in the cold helium jet [11] when the heavier impurity particles form a cluster core which is later covered with lighter impurity particles.…”

“…1(a)) to produce an rf discharge (f = 40-52 MHz, P = = 40-90 W). The typical conditions during sample preparation were as follows: the impurity admixture, , the superfluid helium temperature 1.5 K, and the duration of the sample condensation 600-5000 s. Upon fast cooling of the gas jet, impurity nanoclusters with characteristic size of 5-6 nm form in the gas phase [10,11]. In bulk He II the nanoclusters aggregate into porous condensates with impurity particle densities ~ 10…”

Evidence for high saturation of porous amorphous carbon films by noble gases

“…non-crystallographic multi-shell icosahedra (ico) [13] and Mark's decahedra (dec) [14], with, initially, from one up to twenty shells for every structural type. Such MTPs are known [15][16][17] to appear in open and partly-open geometry due to their energetic preference as compared with fcc (face centered cubic) and hcp clusters. The diffracted intensity (per atom) for each cluster k comprising N k atoms was calculated using Debye formula:…”

“…Diffractograms were analyzed applying the simulations which were similar to those described previously [6,[17][18][19][20][21][22], i.e. basing on the assumption of a wide variety of possible structures and sizes involved in the formation of observed diffraction patterns.…”