Clusters cavity

The relationships between the various structures of the ruthenium, cobalt, and rhodium dicarbido clusters have been discussed in terms of their electron counts and the accommodation of some electrons in MM antibonding orbitals. Such treatments have rationalized the paramagnetism of some clusters via partial occupation of such orbitals leading to swelling of the intra-cluster cavity to a point where the C2 fragment can be accommodated. 

The substitution of H2O ligands coordinated to the molybdenum centres of M0154 by ambivalent and/or multivalent ligands, for example the amino acid cystine can be coordinated to the inner wall of the cluster cavity and hence creates hydrophobic and hydrophilic surroundings with different functionalities (see Figure 14.7) [9]. 

The cluster dianions [Co8C(CO)ig]- (Fig. 8a) and [NigC(CO)i6] provide rare examples of a first-row main-group atom occupying a square antiprismatic cluster cavity,and also illustrate the capacity of carbon to become eight-coordinate. However, on progressing to the heavier main-group elements such as Si, P, S and As we find a propensity for clusters based on the square-antiprism. 

A second independent method of direct absorption spectroscopy has been recently applied to clusters cavity ring down (CRD) spectroscopy. This method, where a sample is introduced into the cavity of a high finesse Fabry-Perot interferometer, and is shown schematically in Fig. 3. 

Nucleation processes within a cluster cavity—from a Mojjg to a Mo24s cluster... 

Symons, R.S. and Vaughan, J.R.M. 1994. The linear theory of the clustered-cavity klystron. IEEE Transactions (Oct.). 

D. Nucleation Processes within a Cluster Cavity—from an Moiye to an Mo248> Cluster... 

Paul J B, Collier C P, Saykally R J, Scherer J J and O Keefe A 1997 Direct measurement of water cluster concentrations by infrared cavity ringdown laser absorption spectroscopy J. Phys. Chem. A 101 5211-14... 

Provencal R A ef a/1999 Infrared cavity ringdown spectroscopy of methanol clusters single donor hydrogen bonding J. Chem. Phys. 110 4258-67... 

A microwave pulse from a tunable oscillator is injected into the cavity by an anteima, and creates a coherent superposition of rotational states. In the absence of collisions, this superposition emits a free-mduction decay signal, which is detected with an anteima-coupled microwave mixer similar to those used in molecular astrophysics. The data are collected in the time domain and Fourier transfomied to yield the spectrum whose bandwidth is detemimed by the quality factor of the cavity. Hence, such instruments are called Fourier transfomi microwave (FTMW) spectrometers (or Flygare-Balle spectrometers, after the inventors). FTMW instruments are extraordinarily sensitive, and can be used to examine a wide range of stable molecules as well as highly transient or reactive species such as hydrogen-bonded or refractory clusters [29, 30]. 

This reduction in activation energy will occur only when the structure of the transition state complex fits well in the zeoHte cavity. This is the case for the protonated toluene example in the zeoHte mordenite channel. The structure of the transition state complex in the cluster simulation and zeoHte can be observed to be very similar to the one in Figure 1.10. 

In the present study, we synthesized in zeolite cavities Co-Mo binary sulfide clusters by using Co and Mo carbonyls and characterized the clusters by extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and high resolution electron microscopy (HREM). The mechanism of catalytic synergy generation in HDS is discussed. 

It was shown by EXAFS that the structure and dispersion of the Mo sulfide species in MoSx/NaY were unaltered by a prolonged sulfidation of 20-h at 673 Kina stream of H,S/Hj. This fact indicates that highly dispersed Mo sulfide species are thermally stable. On the other hand, with MoSx/AljOj prepared by using Mo(CO) [12], a considerable agglomeration of highly dispersed Mo sulfide species was observed at a shorter treatment time. It is considered that highly dispersed Mo sulfide clusters are thermally stabilized in zeolite cavities. 

The size of the deposit depends on the size of the hole and not on polarization time, denoting a certain balance between electrochemical energy and the surface energy of the cluster. This technique has been also employed to study the filling of Au cavities by Bi and Ag. In the latter work, the behavior of Bi is contrasted with that of Ag. While the holes are filled at underpotentials in the first... 

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