Structure of metallic nanowires and nanoclusters formed in superfluid helium

Non-isothermal physical and chemical processes in superfluid helium

“…However, it was expected that due to high thermal conductivity of He II the atoms or small clusters should adhere to each other tightly, forming either monoatomic chains or nanowires with loose fractal structure. Anyway, the nanowires grown in our experiments fortunately were dense, with almost crystalline packing and "large" diameters of a few nanometers, being close to optimal for many chemical and physical applications [16][17][18]. Such a behavior was associated with the existence of the limiting heat flux above which the strong turbulence develops in He II.…”

“…This rate estimates as 10 5 W/cm 2 [16]. We believe that even for nanometer metal clusters the limiting heat flow will be as well significantly lower than that enormously high estimate.…”

“…Indeed, according to our mechanism (see [16] There is no delayed fluorescence in a metal, and the plasmon excitation by a laser lasts during the time much shorter than a nanosecond [24]. The only source of parasitic light in the microsecond time range is the radiation of plasma excited in the focal spot of the laser.…”

“…But it should be compared with the heat removal rate required, for example, to prevent melting of the merging product of two metal balls with 1 nm-diameter each (as it shown [16] the clusters of such size are the "bricks" for nanowire growth in the vortex core). This rate estimates as 10 5 W/cm 2 [16].…”

“…Our model of nanowire formation in He II based on the assumption of adiabatic regime of the coagulation process that leads to the cluster melting [16] has been recognized in several independent studies [21,22]. Nevertheless, we decided primarily to perform the systematic comparison of diameters of the nanowires grown in a low temperature experiments from various metals with those predicted for them by the model [16].…”