Inert Gas Condensation Technique Research Articles

Close-packing structure of small barium clusters.

Barium clusters are produced by the inert-gas condensation technique. The observed size distribution shows large peaks at n=13, 19, 23, 26, 29, 32, as well for singly charged clusters as for doubly and triply charged clusters. These results can be interpreted by icosahedral close-packing structures, similar to those observed in noble-gas clusters.

Electronic properties and fragmentation processes for singly and doubly charged indium clusters

Indium clusters are produced by the inert gas condensation technique. The ionization potentials are found higher for small clusters than for the indium atom. This result is interpreted by the p character of the bonding as in aluminum. The fragmentation processes are studied and discussed. The behavior of the ionization potential explains why the evaporation of neutral monomers is an unlikely channel in the dissociation processes. Finally doubly charged indium clusters are detected for n≥15 and their ionization threshold is determined. Triply charged clusters are also observed.

Fragmentation of singly and doubly charged lead clusters

Lead clusters are produced by the inert gas condensation technique. The fragmentation of singly and doubly charged clusters is studied as a function of the electron energy. For singly charged clusters our results indicate the successive loss of neutral atoms. For doubly charged clusters, the smallest observed cluster corresponds to the smallest neutral cluster generated in the beam. Moreover, we show that the critical size previously observed at n c= 31 may be explained by fragmentation processes.

Phase Control in Nanophase Materials Formed from Ultrafine Ti Or Pd Powders

ABSTRACTThe effect of He gas pressure during evaporation and post-evaporation O2 exposure on phase formation in nanophase materials has been examined. Ultrafine powders of Ti and Pd were prepared by the inert gas-condensation technique and bulk nanophase samples were formed by consolidation of these powders with or without prior exposure to O2. Evaporation of Ti in He pressures greater than 500 Pa followed by exposure to O2 results in the formation of ultrafine powders of crystalline rutile (TiO2) which are compacted to form nanocrystalline TiO2. Surprisingly, reducing the He pressure used during evaporation to less than approximately 500 Pa results in the formation of ultrafine powders of an amorphous phase. Room temperature consolidation of this powder under vacuum, however, results in nanocrystalline Ti being formed if the powder is not exposed to O2 prior to consolidation, and a mixture of rutile and an unidentified crystalline phase if the powder has been previously exposed to O2. Further reduction of the He pressure during evaporation of Ti to less than approximately 10 Pa results in the formation of crystalline Ti having a film-like morphology rather than than the desired ultrafine particles. Experiments on Pd evaporated in 10 to 6000 Pa of He have yielded ultrafine powders and consolidated samples of only the crystalline fcc phase, regardless of the He pressure

Velocity slip measurements of bismuth clusters produced by the inert gas condensation technique

The velocities of bismuth clusters produced by the inert gas condensation technique have been measured by the time of flight spectrometer. A large velocity slip has been observed between the helium carrier gas and the clusters. The translational temperature of helium has been also measured. Although the fragmentation phenomena associated with electron impact ionization precludes a precise determination of the temperature of the clusters, this temperature can be roughly estimated and our results show that a partial mass selection of neutral clusters by a velocity selector is possible.

Magnetic phase transitions in nanocrystalline erbium

Nanocrystalline samples of 99.9% pure erbium with particle sizes between 10 and 70 nm have been produced by the inert gas condensation technique. Magnetic susceptibility measurements on samples compacted to between 50% and 75% of bulk density indicate a modification in the high-temperature phases and superparamagnetic behavior at low temperatures. ESR signals near g=10 are probably due to Er compounds which may form during the production process.

Generation of silver cluster using the inert-gas condensation technique-observation of doubly charged clusters

Mass spectra of Agn aggregates (2<n<or approximately=45) have been obtained using the inert-gas condensation technique: the mass analysis is performed by electronic time-of-flight spectrometry including electron-impact ionisation. The intensities of single ionised clusters exhibit odd-even alternation:I(Ag2n+1+)>I(Ag2n+). Doubly charged clusters have also been detected and evidence exists for a Coulomb explosion mechanism.

Production and Properties of Atomic and Molecular Microclusters

AbstractThis review reports on the microcluster research at Konstanz University. Metallic and ionic microclusters are produced by an inert gas condensation technique, while clusters from different gases are obtained by adiabatic expansion. An electronic time of flight‐mass‐spectrometer is used for cluster detection. Fragmentation processes, pronounced intensity distributions and the disintegration of multiple charged microclusters are discussed. An example of intramolecular reaction in organic clusters is given.