Clusters laser ablation

An indication of the range of such clusters which might possibly be synthesized is given by the observation that mass spectroscopic analysis of the products of laser-ablation of CoS... 

Uneven open shell Pn clusters are easier to ionize than even closed shell ones and the stability of the closed shell uneven P cluster cations is higher. For very large Pn+ cations with n = 25 + 8x (x — 0.1.2. 8) islands of stability were observed in the time of flight mass spectrum (TOF-MS) obtained by laser ablation of red phosphorus, suggesting that the more stable P clusters have connections with units of eight P atoms [71d]. A lot of effort has been put into the calculation of the most stable Pn+ cation structures. The respective global minimum structures of the more stable uneven P3+, Ps+, P71 and P<)h cluster cations are shown in Figure 2.6-10 [73, 74],... 

Cluster ion sources with different production techniques have been devised [10]. The cluster ions are produced, for instance, by vaporizing the materials using a heated oven, a laser ablation apparatus, or sputtering. Essential features of the cluster ion source are increased intensity and stability of the beam, and control of the mass distribution of the particles. Further development of cluster ion sources is in progress at several facilities [7,11]. 

Femtosecond infrared strong field ionisation of metal clusters produced by kHz laser ablation... 

There is mass spectroscopic evidence for clusters C59B, C68B2,. ..C54 B6 in the products of laser ablation of boron nitride/graphite composites (Guo et al. 1991). It is proposed that these may be versions of the fullerene cage in which heteroatoms have occupied carbon sites with little disturbance of the framework. This is a plausible hypothesis for low doping ratios, in view of the ability of carbon to substitute for boron in carboranes. Bond-energy considerations suggest that... 

Kneipp et al. [34] showed that enhancement is independent of cluster sizes ranging from 100 nm to 20 pm. The data and the electron microscope images of the SERS particles are depicted in Figure 10.8 together with the nonresonance SERS spectrum of 10 6 M crystal violet. SERS enhancement is estimated to be on the order of 106 for the spatially isolated cluster and up to 108 for the colloidal clusters. The isolated silver clusters were made by the laser ablation technique mentioned earlier. 

Recently, a laser ablation-condensation technique was used to produce nanometer-sized catalyst clusters to grow nanowires by the VLS method. A schematic of the laser ablation apparatus used by Morales and Lieber (1998) to produce silicon nanowires is shown in Fig. 11. The target consists of silicon and the catalyst material (e.g., Sii AFeA), and a pulsed laser is used to produce nanometer-sized catalyst clusters within a reaction chamber at 1200°C. The ablated materials are carried by an argon gas flow, and the... 

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