cm"1 2)in TEA (where Chi a-Ll occurs), despite superior resolution (Figure 3).The number of extra ligands should evoke some changes in the vibronic structure, since an axial shift of the Mg atom takes place, and the charge is redistributed in the central part of the Chi a molecule as in the case of PChl. Indeed, for the monoligated form the 6 values of 567, 601, 877, 912, 1004, and 1122 cm"1 seem to be characteristic (Figure 3). Alternatively, in the Chi a•L2 spectra the u>e of 592 and 616 cm"1 arise and the 6 = 982 peak diminishes (Figure 6). It may be noticed that the respective o>e values are very close in pyridine, 1-butanol, and methanol-ethanol,28 while a slightly different set is seen in TEA, ether,9 DMF, and -collidine (spectra not shown). Therefore, the spectral changes are dependent on the Chi a solvation state rather than on a specific host, and the solvates with different Mg coordination This article not subject to U.S.

No abstract

knowledge of the nature of supported metal oxide catalysts, it cannot yet be concluded whether or not this complex condition of the vanadium catalyst is related to the layered structure. However, we can indicate that the chemical affinity to crystal faces and/or the crystallographic fitness may influence surface condition, as mentioned below.The coverage behavior of vanadium oxide was related to the electronegativity of cations in its oxides, and some relationship with the surface acid-base properties might also be indicated.9 Because the acidic oxide (i.e., V205) was effectively supported on the basic support, such differences in the acid-base properties could be the cause of the high coverage efficiency of vanadium oxide. In other words, the vanadium oxide could be supported due to the different chemical property of the support. Therefore, vanadium oxide may be supported on alumina with the strongest interaction with the support. In this condition, it may not be easy to form the layer structure of vanadium oxide. On the other hand, when there is little interaction with the support as on Si02, va-nadium oxide behaves as if it were unsupported. After all, high exposure of the active (010) face on Zr02 and T:02 could be understood as resulting from the medium degree of interaction with the support.The high exposure of active V=0 sites on Ti02 (anatase) was explained on the basis of the crystallographic fitness between anatase and V205, as was indicated by Courtine et al.16 This explanation is significant in the case of anatase. Such a crystallographic fitness could be observed on Zr02 and Ti02 (rutile), since vanadium oxide on these supports exposed active sites similarly on the anatase. On these oxides, however, some alterations of crystal dimensions in the boundary may stimulate the fitness as was indicated for V205 on Ti02 (rutile).3a Acknowledgment. This work was supported by a Grant-in-Aid from the Ministry of Education, Science, and Culture, Japan (No. 59470097).

No abstract

The effect of the addition of molecular nitrogen on the oxygen dissociation is investigated in a low pressure gas discharge. The dissociation efficiency is measured as a function of N2 concentration, for a total pressure ranging from 0.4 to 3 Torr in discharge tubes with diameter between 6 and 21 mm. The concentration of O atoms is obtained by the NO+O chemiluminescent reaction. The authors show that for a few percent of nitrogen the oxygen dissociation degree varies by a factor of 1.5-10 depending on the nitrogen concentration, tube diameter and total pressure. The ratio of the dissociation degree for pure oxygen and mixtures of oxygen and nitrogen is calculated, and the authors show that their results imply that, as the tube diameter tends to infinity, the dissociation efficiency tends to one. The authors conclude that the most important reason for the increase in the dissociation of oxygen in the presence of nitrogen is the reduction of wall diffusion losses.