Inert Gas Clusters Research Articles

The fragmentation of molecular ions in association with large inert gas clusters

The unimolecular decomposition of single ethylene ions in association with argon clusters containing more than 100 atoms has been observed. Fragmentation on these large clusters provides strong support for the proposal that a charge-transfer mechanism is responsible for exciting the molecular ions. In addition, the results show evidence of enhanced fragmentation for those molecular ions associated with a “magic number” of inert gas atoms. From these observations it is suggested that reactant ions lie on, or close to, the surface of a cluster.

Vibrational predissociation induced by exciton trapping in inert-gas clusters

The dynamics of exciton trapping, vibrational energy transfer and vibrational predissociation in an electronically excited state of Ar 13 clusters was explored by classical molecular dynamics. Two distinct time scales were established for vibrational energy flow, which result in a molecular-type, reactive dissociation process of Ar atoms for this cluster.

Formation of helium platelets in molybdenum

Over the past two decades, helium introduced into metals either by ion implantation or by the (n, α) reaction has been studied over a wide range of concentrations and temperatures1,2. Early studies were relevant to fission reactor technology3,4 but more recent emphasis has been on the role of helium in fusion reactor environments. One area of interest concerns the interaction of helium ions from the plasma with the first-wall surface while the influence of the helium from the (n, α) reaction on void nucleation, and on grain boundary bubble nucleation, is also under investigation5. One long-established property of insoluble helium and other inert gases in metals is their tendency to precipitate as bubbles. However, the inference that inert gas clusters always assume a three-dimensional form may not be justified. We present here experimental evidence showing that, at least in molybdenum, helium can initially aggregate in an unexpected planar form. Furthermore, we have found a bubble nucleation route involving the formation of several small bubbles from a single helium platelet.

Spectroscopy of large molecules in inert gas clusters

Aromatic hydrocarbons provide nucleation centers for the formation of clusters of inert gases in high-flow supersonic beams. Large clusters of Ar, each containing a single tetracene (T) molecule, were prepared by supersonic expansion of the seeded gas at pressures p = 3000–13000 Torr and interrogated by laser-induced fluorescence spectroscopy Evidence is reported for homogeneous line broadening of large TAr n clusters prepared at p⪖ 8000 Torr.