Crystals spectra

Figures Raman spectra of crystalline and glassy potassium digermanate showing comparison between crystal spectra and glass spectra.

Polarised low-temperature crystal spectra of inorganic complexes. P. Day, Angew. Chem., Int. Ed. Engl., 1980,19, 290-301 (36). 

As was the case with lanthanide crystal spectra (25), we found that a systematic analysis could be developed by examining differences, AP, between experimentally-established actinide parameter values and those computed using Hartree-Fock methods with the inclusion of relativistic corrections (24), as illustrated in Table IV for An3+. Crystal-field effects were approximated based on selected published results. By forming tabulations similar to Table IV for 2+, 4+, 5+ and 6+ spectra, to the extent that any experimental data were available to test the predictions, we found that the AP-values for Pu3+ provided a good starting point for approximating the structure of plutonium spectra in other valence states. However,... 

Spectroscopic analysis of Pu5+ and Pu6+ halides is in its initial stages. No low-temperature single-crystal spectra have been reported. A 25°C mull spectrum of the compound Rb2PuF7 was described earlier (37), and is now supplemented by the results for CsPuFg (31) PuF gas-phase spectra have been reported by several different groups at ANL (38-39). 

A crystal-structure determination on [Ni(PhCH2CS2)2] showed evidence of a Ni-Ni bond (Ni—Ni distance, 256 pm) in a bridging, acetate-cage, binuclear complex (363). Each nickel atom is 5-coordinate and is in a tetragonally distorted, square-pyramid spectroscopic evidence for a Ni-Ni bond has been obtained (364). The polarized crystal spectra showed more bands than predicted for a mononuclear, diamagnetic, square-planar nickel(Il), and the spectra are indicative of substantial overlap of the d-orbitals between the two nickel atoms. The bis(dithiobenzation)nickeKII) complex was found to exhibit unusual spectrochemical behavior (365). 

Most of the information content from ESR spectra of organometallic radicals and coordination complexes comes from dilute single-crystal spectra or frozen solution spectra. Nonetheless, there are some bits of information and applications that come uniquely from isotropic spectra, and we discuss those aspects in this chapter. 

Mixed-Crystal Spectra, Model Calculations in the Theory of (Craig). ... 

The electronic spectra of bis(acetylacetonato)-copper(II) and its derivatives have aroused controversy for about twenty years. In spite of much effort, polarized crystal spectra have not led to definitive assignments. Hitchman (124) has attempted to shed some light on the problem by comparing the crystal spectra of [Cu(acac)2] and its quinoline adduct, using the AOM to determine how the addition of a quinoline molecule should affect the spectrum. He concluded that the energy sequence dvv >d,2 >... 

A96 Butler, I. S., Shaw, C. F. J. Raman. Spect. 3, 65 (1975) Raman and IR solution and crystal spectra ofW(CO)4NOBr are analyzed (data from natural abundance 13CO-containing species are included)... 

The best conclusion one can draw, then, seems to be that comparisons between mineral and glass Mossbauer parameters are qualitative as far as coordination number and site symmetry in the glass are concerned. However, the crystal spectra are interesting for their own sake. 

When KMnO is mixed with MnCl2,4H20 in cone. HCl followed by the addition of [Co(en)3]Cl3 at — 10"C, [Co(en)3][MnCl ],H20 is formed. Spectroscopic and magnetic properties = 4.94 BM at 293 K) have been reported. Polarized crystal spectra of MnClj" have been reported. The results indicate 2, symmetry for (bipH2)[MnCl5] (bipH2 = bipyridinium ion) and symmetry when Mn is doped into (Et N)2lnCl5. ... 

Intensity dependence on rhombic distortion at Fe(IIl), 36 226-229 NIR CT bands, 36 217-220 polarized single-crystal spectra, 36 221-222... 

The optical properties of amorphous solids are interesting. These solids are optically isotropic. Furthermore, the sharp features present in crystal spectra are absent in the spectra of amorphous solids even at low temperatures. The overall features in the electronic spectra of amorphous solids (broad band maxima) are, however, not unlike those of crystals, reflecting the importance of short-range order in determining these characteristics. The optical absorption edges of amorphous materials are not sharp and there is an exponential tail in the absorption coefficient (Fig. 7.13) associated with the intrinsic disorder. 

The assignments of the spectra of suitable nickel(II) complexes on the grounds of the theory roughly described (160,161) are on the whole impressively accurate, but in certain cases errors of over 30% may mean either that the purely electrostatic picture is not good enough, or that adjustment of the parameters would improve the agreement. Measurements of crystal spectra (72) have shown some of Maki s assignments to be unlikely. 

In the case of dibenzene chromium and its cation, the most complete investigation of the electronic spectra is due to Yamada and co-workers (76) who report both solution and crystal spectra in detail for dibenzene chromium iodide and ditoluene chromium iodide. Four intense bands were observed in the region 3 to 6 eV, and a detailed discussion of these in terms of molecular-orbital assignments has been given by Berry (78), although no direct comparison with the energy-level scheme of Shustorovich and Dyatkina (75) is reported. The intense band at 5.51 eV (log max = 4.14) for... 

IV, EXPERIMENTAL SPECTRA AND THEIR ANALYSIS A. Single-Crystal Spectra... 

PCtossium bifluoride crystals. Spectra at 293 and 90°K. Tne dotted curves relate to disordered layers... 

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