Yttrium atoms

Fig. 9. Time-of-flight spectra for non-reactively scattered yttrium atoms at indicated lab angles for the Y + CH3OH reaction at Eco = 28.1 kcal/mol. Fits data generated using the CM distributions shown in Fig. 10.

Fig. 10. (a) Lab angular distribution for non-reactively scattered yttrium atoms from... 

The 1-2-3 superconductor has a perovskile-like structure (7.33a,c). There are systematic oxygen atom vacancies in the unit cell compared to a stack of simple perovskite unit cell (Fig. 7.33b). These occur between adjacent copper atoms in the chains along the c axis. The vacancies are in the yttrium atom plane. There are also vacancies between copper atoms along the a axis in the copper-and-oxygen planes... 

What does transition mean A transition is a change from one thing to another. Yttrium (atomic number 39) is a very different metal from silver (atomic number 47). Even though the transition elements are all metals, Group 3 metals act very differently from Group 12 metals. 

Infrared spectroscopy measurements on YB66 reveal a strong absorption band around 130 cm-1 which is though to be due to the local vibration of yttrium atoms (Werheit et al., 1991). 

A low-temperature X-ray diffraction study has been carried out on the monomeric bis(trimethylsilyl)methyl derivative [Me2Si(OfBu)(NfBu)]2YCH-(SiMe3)2 (69b) (Fig. 22) [27], The coordination geometry around the central yttrium atom can be described as distorted trigonal-bipyramidal with two... 

A mixed metal siloxide complex YCu(OSiPh3)4(PMe2Ph) was obtained by a simple addition reaction (Eq. 3) [48], The geometry around the yttrium atom is distorted tetrahedral. The molecule is cleaved in solution by Lewis basic solvents like THF. 

The generation of reactive species by a fast pre-reaction is a well established process in kinetics, particularly in flow systems, although this technique is now being used in molecular beam sources [see (f), below]. As atoms are commonly generated by thermal or microwave dissociation (see above), reactions are mainly used to produce radicals. However, some atoms may be produced by reaction as a more convenient alternative to direct vaporisation or dissociation. Scandium and yttrium atoms have been generated [25] by the reaction... 

In this respect, it can be noted that the oxygen diffusion supply through SFs areas of 124 or 247 can be neglected (due to the relatively small diffusion coefficient (D 0(i24)ab, Table 1). It is also relevant to emphasize that (as it is seen from Table 1) the diffusion redistribution of barium and yttrium atoms in the 123-matrix (which is necessary for flowing of step (3)) is possible only in the close vicinity of the 211 precipitates. 

However, in the solid state, the evidence for the endohedral nature of the contradictory results were reported for extended X-ray absorption fine structure (EXAFS) experiments on an impurified extract of Y Cs2 (i.e., a mixture of Y Cs2 and empty fullerenes). Soderholm et al. (1992) reported that the yttrium atom is exohedrally attached from the outside to the Cs2 cage, whereas Park et al. (1993) reported an endohedral nature of Y Cs2 the nearest-neighbor C-Y distances obtained were 2.53 0.02 and 2.4 A, respectively. Kikuchi et al. (1994a) performed an EXAFS experiment on a purified La Cs2 powder material and reported that the nearest-and next-to-nearest-neighbor C-La distances are 2.47 0.02 and 2.94 0.07 A, respectively. 

The CV measurements indicate that the oxidation state of the yttrium atom in Y Cs2 (Suzuki et al., 1996) was close to that of La Cs2, probably 3-i. The electrochemistry of Y Cs2 is almost identical to that of La Cs2 (Anderson et al., 1997a Suzuki et al., 1996). Other mono-metallofullerenes such as Y Cs2, Ce Cs2 and Gd Cs2 have a similar tendency in their redox properties (Suzuki et al., 1996). Anderson et al. (1997b) reported CV data on Sc3C2 Cso- CV measurements were also taken on other lanthanide fullerenes such as Pr Cs2, Nd Cs2, Tb Cs2, E)y C82, Ho C82, Er C82 and Lu C82 by Wang et al. (1997). The first reduction potentials of all seven M C82 were found to locate within a close vicinity... 

The monometalhc endohedral fullerenes are typified by M C82 (M = Sc, Y, La), and ESR studies of these molecules indicate that they are best described as the charge-separated species M + C82 For all three species, two distinct signals are seen, indicating the presence of two isomers of M C82, although it is not known whether these correspond to any of the observed isomers of the parent ffillerene C82 EXAFS studies of Y Cs2 indicate that each yttrium atom has seven nearest neighbor carbon atoms at 2.35 A as well as another yttrium atom at 4.05 A. These data are not consistent with a simple endohedral structure and further studies are required to clarify this apparent contradiction. 

The structure of the deprotonation product 3a, in which the yttrium atom is part of a four-membered Y-Cll-Sil-Nl ring, is shown in Fig. 2. The carbanionic Cll atom shows a distorted trigonal bipyramidal coordination, the axial and equatorial positions being occupied by Y, K [with K-Cll-Y 176.36(18)°, and the two H atoms and Sil, respectively. The potassium cation exhibits a pseudo-tetrahedral coordination by the Cl 1 atom, the centroids of two benzene rings, and one intermolecular agostic contact to the carbon atom of an adjacent trimethylsilyl group. 

The lanthanide series of metals includes the 15 elements with atomic numbers 57-71, plus yttrium (atomic number 39). The lanthanides occur in the earth s crust at concentrations exceeding some commonly used industrial elements making the term rare earths something of a misnomer. For example, yttrium, cerium, lanthanum, and neodymium are present in the earth s crust at higher concentrations than lead. Of the 15 lanthanides, only promethium does not occur in nature - it is a man-made element. All of the lanthanides have similar physical and chemical properties. Because of similarities in their chemistry and toxicity, the characteristics of the lanthanides are often described as a group. Within the lanthanide group, however, there are differences between the toxicity of the individual lanthanide elements and their compounds. 

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