Carbon clusters method

Graphitic sheets, however, are not detectable in the carbon-plasma by ion chromatography (IC) [162, 174, 183-185]. This method provides a means for separating carbon cluster ions with different structures because the reciprocal of the ion mobility is proportional to the collision cross-section. Several species with different structures coexist and their relative amount depends on the cluster size. Small clusters (n < 7) are linear. In the range n = 7-10 chains as well as monocycles coexist. The clusters C are exclusively monocycles and the range... 

Besides the carbon cluster ions, carbide cluster ions are formed in different plasmas with remarkably high ion intensities. The abundance distribution of these carbide cluster ions as a function of cluster size has been observed to be very similar using the different sohd-state mass spectrometric methods, with higher intensities for cluster ions with even numbered carbon atoms than for neighbouring... 

A characteristic feature of the carbon modifications obtained by the method developed by us is their fractal structure (Fig. 1), which manifests itself by various geometric forms. In the electrochemical cell used by us, the initiation of the benzene dehydrogenation and polycondensation process is associated with the occurrence of short local discharges at the metal electrode surface. Further development of the chain process may take place spontaneously or accompanied with individual discharges of different duration and intensity, or in arc breakdown mode. The conduction channels that appear in the dielectric medium may be due to the formation of various percolation carbon clusters. 

IR, Raman, NMR, ESR, UPS, XPS, AES, EELS, SIMS) [1]. However, some industrial carbon materials such as amorphous carbon films and carbon black cannot be easily characterized from the local-structure point of view by these methods, because these materials usually take amorphous and complex structures. Recently, soft X-ray emission and absorption spectroscopy using highly brilliant synchrotron radiation [2] has been utilized to characterize various carbon materials, because information on both the occupied and unoccupied orbitals, which directly reflect the local structure and chemical states, can be provided from the high-resolution soft X-ray measurements. We have applied the soft X-ray spectroscopy to elucidate the local structure and chemical states of various carbon materials [3]. Additionally, we have successfully used the discrete variational (DV)-Xa method [4] for the soft X-ray spectroscopic analysis of the carbon materials, because the DV-Xa method can easily treat complex carbon cluster models, which should be considered for the structural analysis of amorphous carbon materials. 

Naturally, group 4 elements are again the focus of interest. Structures of hydrocarbons (which maybe thought of as partly or completely passivated carbon clusters) have been optimized by Hobday and Smith [65]. Hydrogen-passivated silicon clusters have been studied a few times, for example by Chakraborti and coworkers [97,98] at the TB level, as well as by Ge and Head [99] at the semiem-pirical Austin method 1 (AMI) level, with DFT and MP2 refinement calculations they noted a marked influence of the passivation layer on cluster structures, with Si10H16 and Si14H20 already exhibiting bulk structure, in stark contrast to bare silicon clusters. 

The first applications of ion mobility methods to obtain structural information of polyatomic ions were on cluster ions, that is carbon [1-5] and silicon [6, 7] cluster ions. In carbon clusters atoms are bound to each other by covalent bonds, leading to structures like chains for small clusters (<10 atoms), rings, polycyclic... 

The mass determination of ionic species (atomic or polyatomic ions) in mass spectrometry is always a comparative measurement, which means the mass of an ionic species is determined with respect to reference masses of elements (or substances) used for mass calibration. The reference mass is thus acquired from the mass unit (m = In = 1/12) of the mass of the neutral carbon isotope (m = 1.66 X 10 kg). A mass calibration is easy to perform in solid-state mass spectrometry if the sample contains carbon (using carbon cluster ions with whole masses, as discussed above). The so-called doublet method was apphed formerly, e.g., ions and doubly charged Mg + forming a doublet at the same nominal mass number 12 were considered, where they are slightly displaced with respect to one another. The doublet method is no longer of relevance in modern inorganic mass spectrometry. Orientation in the mass spectra can be carried out via the matrix, minor and trace elements after mass calibration and by comparing the measured isotopic pattern of elements with theoretical values. 

It had been expected, before the first macroscopic production and extraction of La Cs2 (Chai et al., 1991), that metallofullerenes based on the Cgo cage would be the most abundant metallofullerenes that were prepared in macroscopic amoimts, as was the case in empty fullerenes. This is simply because that Ceo is the most abundant fullerene which can be easily produced by either the arc-discharge or the laser furnace method (cf. Section 2.1). In fact, an earlier gas phase experiment on the production of carbon clusters containing La via the laser-vaporization cluster-beam technique (Heath et al., 1985) indicated that La Cgo is a prominent "magic number" species among various La C (44 < n < 80) clusters (Figure 1). 

Recent chemical experiments with transactinides have been carried out by application of refined methods. Fast transport is achieved by thermalizing the products of nuclear reactions recoiling out of the target in helium gas loaded with aerosol particles (e.g. KCl, M0O3, carbon clusters) of 10 to 200 nm on which the reaction products are adsorbed. Within about 2 to 5 s the aerosols are transported with the gas through capillary tubes over distances of several tens of metres with yields of about 50%. 

Liang, C. Schaefer, H.F., III. Carbon clusters The structure of Cio studied with configuration interaction methods. J. Chem. Phys. 1990, 93(12), 8844-8849. 

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