Rare gas supports

One of the objectives of this paper is to evaluate the spectroscopic and photochemical consequences of the occurrence of markedly disparate guest-host interactions in the ground and optically excited states of Cu and Ag atoms, and some of their low nuclearity clusters, in rare gas as well as other supports. Original papers should be consulted for details. 

In a few cases, adsorption on particulate nickel has been studied other than in the form of the conventional oxide-supported metal catalysts. Nash and De Sieno (73) exploded nickel wires in a rare-gas atmosphere to give Ni particles of ca. 20-nm diameter. Results were reported (but not illustrated) characterizing adsorption of ethyne they are similar to those found by Eischens and Pliskin. 

The He2A 2 state has nearly the same dissociation energy as the He (22J ion. This supports the idea that the excited He2 configurations can be described at small interatomic distances as an inner He core with an outer Rydberg orbital. This description is less quantitative for the heavier rare-gas pairs. The unusual maxima result either from curve crossing (e.g., C S ) or as for the state by a changeover in the... 

Intrazeolitic and Rare Gas Isolated Silver Atom and Silver Cluster Spectroscopy, Photoprocesses, and Support Interactions... 

In the past five years, the field of metal-zeolite chemistry has developed to the point where a number of metal atomic and small cluster guests have been synthesized and unequivocally characterized by spectroscopic and crystallographic techniques. The silver-zeolite A, X and Y systems in particular have yielded a wealth of valuable structural and site information pertaining to silver guests in the size range of one to six atoms (3). The spectroscopy of these silver-zeolites can therefore be probed in detail and compared with the corresponding data for silver atoms and silver clusters immobilized in weakly interacting rare gas solid supports (4). 

At this point we note that the overall form of the absorption, fluorescence emission and excitation profiles for Agx, Ag + and AgP+ for AgxNaX and AgxNaY is superficially reminiscent of those observed for Ag°, Ag2 0, and Ag3 ° entrapped in rare gas solids (4-10). However, a number of important differences are also apparent. These details are discussed for each silver guest as a necessary prelude to the subject of metal-support interactions. 

E) Support Interactions in the Spectroscopy and Photoprocesses of Ag,+ in Zeolite X and Y It is interesting to compare the spectroscopic properties of site I, I isolated Agz in ZY with those for Agz entrapped in rare-gas solids (6). In the latter one finds a strongly blue shifted gas to matrix X,... 

It is apparent from the support sensitivity of these low lying electronic transitions that guest-host interactions play a significant role for Ag3 ° and Ag3° in rare gas... 

Unlike molecular solvents, charge-dipole interaction cannot be expected between closed-shell atoms and excess electrons. However, finite and infinite ensembles of rare-gas atoms can support a bound and/or quasi-bound state for electrons, due solely to the collective polarization of the surrounding atoms. In bulk Xe, for instance, the conduction band lies 0.7 eV below the vacuum level [62]. The formation of negatively charged clusters has also been reported for He [35 37], Ne [38]... 

As mentioned above, rotations play a major role in CET. Most of the CET occurs via a T/R mechanism in which the translational energy goes into rotation. This is confirmed in a detailed study of single mode excitation [14] where each mode of the benzene was pumped separately. It was found that the values of a]i are a factor of 3-5 larger than the values of d- The conclusion that rotations are the major contributors to the values of an in all specific-modes excitation energies is supported by the work of Rosenblum etal. [15] who found that in SO2 rare gas collisions, rotations are the major energy transferring mode. 

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