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An instrument for the synthesis and analysis of nanoparticles and ultrathin films of Pu and other actinides has been constructed. To facilitate the production of nanoscale specimens of these materials, pulsed laser ablation was chosen for the deposition process. The highly toxic and radioactive nature of these materials created a challenging safety environment that needed to be addressed before any work could begin. Particular attention has been paid in this respect towards our future work with plutonium, though the design structure presented here would work equally well with other nonradioactive toxic or reactive materials. The analytical capabilities of the instrument include in situ photoelectron spectroscopy, low energy electron diffraction, scanning tunneling microscopy, and scanning tunneling spectroscopy. The instrument design and first results will be discussed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The intense, ultra-fast electronic excitation of clean silicon (100)-(2 × 1) surfaces leads to the formation of silicon nanostructures embedded in silicon, which photoluminesce in the yellow-green (∼ 2-eV band gap). The silicon surfaces were irradiated with slow, highly charged ions (e.g. Xe[sup 44+] and Au[sup 53+]) to produce the ultra-fast electronic excitation. The observation of excitonic features in the luminescence from these nanostructures has recently been reported. In this paper we report the dispersion of the excitonic features with laser excitation energy. A phonon-scattering process is proposed to explain the observed dispersion. [ABSTRACT FROM AUTHOR]

The emission of small (hydrogenated) carbon cluster ions CnH m + ( n =2-22) upon highly charged Xeq+ ( q =20-44) impact on C84 surfaces is studied by means of time-of-flight secondary ion mass spectrometry. The respective stage of hydrogenation/protonation of a certain carbon cluster ion C n + is a strong indication for its geometrical structure. From the cluster ion yield as a function of cluster size it can be concluded, that the hydrogenation takes place after the initial carbon cluster formation. The carbon clusters seem to be emitted as an entity in agreement with “equilibrium” and “shock wave” models. [ABSTRACT FROM AUTHOR]

Cluster ion emission from a variety of surfaces upon impact of highly charged ions is investigated by time-of-flight secondary ion mass spectrometry. The yield of cluster ions as a function of cluster size for and surface follow a power law decline with exponent approaching the -2 limit of the ”equilibrium” and ”shock wave” cluster emission models. While the decline of the cluster ion emission with cluster size is an exponential decay for highly oriented pyrolytic graphite upon impact, the decline is more gradual than for impact, such that at the relative cluster yield is 1000 times higher. [ABSTRACT FROM AUTHOR]

Depth profiles of [sup 1]H and [sup 2]D in rapidly grown KD[sub 2x]H[sub 2(1-x)]PO[sub 4] single crystals are studied by elastic recoil detection analysis. Results show that, under ambient conditions, deuteration in the first ∼500 nm from the sample surface significantly decreases within the first several days after D[sub 2]O surface polishing. This effect is attributed to deuterium–hydrogen exchange. The effective diffusion coefficient of this process is strongly dependent on both the degree of deuteration and the sample growth conditions. Physical mechanisms of D/H exchange are discussed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Observes the fullerene cage opening on silicon(111) by scanning tunneling microscopy. Correlation between silicon-carbon bonding and fullerene cage opening; Effect of thermal annealing on fullerene clusters; Agglomeration of opened clusters on the surface.

The first hydrodynamic instability growth measurements with three-dimensional (3D) surface-roughness modulations were performed on CH shell spherical implosions at the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 43, 2841 (2004)]. The initial capsule outer-surface amplitudes were increased approximately four times, compared with the standard specifications, to increase the signal-to-noise ratio, helping to qualify a technique for measuring small 3D modulations. The instability growth measurements were performed using x-ray through-foil radiography based on time-resolved pinhole imaging. Averaging over 15 similar images significantly increased the signal-to-noise ratio, making possible a comparison with 3D simulations. At a convergence ratio of ${\sim}2.4$, the measured modulation levels were ${\sim}3$ times larger than those simulated based on the growth of the known imposed initial surface modulations. Several hypotheses are discussed, including increased instability growth due to modulations of the oxygen content in the bulk of the capsule. Future experiments will be focused on measurements with standard 3D ‘native-roughness’ capsules as well as with deliberately imposed oxygen modulations. [ABSTRACT FROM AUTHOR]