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71.
72.
A UPS study of various conducting polypyrrole films is presented. Most of the valence band features can be explained by states derived from the orbitals of the pyrrole monomer and the associated anion molecules. In close vicinity of the Fermi energy, a density of states is observed which decreases linearly towards EF. The corresponding states are introduced by oligomer formation. The π-electronic density at EF is reduced by at least two orders of magnitude compared to ordinary sp-metals. The UPS spectra are consistent with short conjugation lengths and large amounts of disorder, but the corresponding defect states can not directly be observed. 相似文献
73.
Photoelectron and Auger electron measurements have been made on polycrystalline films of sodium metal evaporated in ultra high vacuum, and on Na2O produced by in-situ oxidation by dry oxygen. Most of the spectra were recorded using Mg Kα (1254 eV) radiation but excitation by 5 keV electrons or monochromatized Al Kα (1487 eV) X-rays was used for specific purposes. Core and valence electron binding energies, photoionization cross-sections relative to Na 1s, KLL and KLV Auger energies and transition probabilities are reported. Energy losses in the metal and oxide are discussed and the relative intensities of surface and bulk plasmon losses have been used to calculate mean electron escape depths in the metal. When corrections were made for experimental geometry, escape depths of 10 Å at 180 eV and 31 Å at 1200 eV were obtained. An escape depth of 23 Å at 980 eV was obtained by Na 1s-Na K-Auger intensity correlation and this is consistent with the plasmon data. Data on Auger satellite lines are presented and, in particular, evidence has been obtained which indicates that a high energy satellite should not be attributed to a plasmon gain mechanism. Valence band influences on the KLV Auger spectra are discussed with reference to the XPS spectrum and other sources of valence band information. Unexpected structure was found in the KLV spectra of the metal which, pending thorough interpretation, offsets the sensitivity and resolution advantages which these spectra otherwise offer for valence band studies. 相似文献
74.
J.B. Goodenough G.B. Street Kenneth Lee J.C. Suits 《Journal of Physics and Chemistry of Solids》1975,36(5):451-455
A study has been made of the effect of 3d transition element substitution on the magnetic moment and Curie temperature of MnGaGe. Substitution of 3d elements with atomic number less than Mn (i.e. Ti, V, or Cr) cause relatively small changes in magnetic properties, whereas substitution of Fe, Co, Ni and Cu cause a large reduction in moment and Curie temperature, e.g. substitution of 5 at.% Fe for Mn causes the moment to decrease by 30 per cent. The moment and ferromagnetism of MnGaGe are described in terms of a band model involving both strongly correlated and intinerant 3d electrons. The effect of 3d element substitution may be qualitatively understood in terms of this model. 相似文献
75.
76.
LetX be a set ofv + 1 elements, wherev 0 or 1 (mod 3). If two copies of the collection of
triples chosen fromX can be partitioned intov + 1 mutually disjoint two-fold triple systems, each based on a differentv-subset ofX, we say they form an overlarge set of two-fold triple systems, denoted byOS(TTS(v)). In this paper, we give the first construction of anOS(TTS(10)). We then investigate the properties of the uniqueOS(TTS(6)) and obtain:
Supported by NSERC grant A8651. 相似文献
(i) | A partition of the set of 84 distinctTTS(6) based onX = {1, 2,..., 7} into 12 parallel classes, that is, into 12OS(TTS(6)) each containing sevenTTS(6); |
(ii) | A resolution of the set of 1008 distinctOS(TTS(6)) based onX into 84 parallel classes; |
(iii) | Simple constructions of several strongly-regular graphs, including both the Hoffman-Singleton and Higman-Sims graphs, which arise from the relation between the family of 84 distinctTTS(6) and the family of 30 distinctSTS(7), all based onX. |
77.
Summary AK
4–e design of ordern is a pair (S, B), whereB is an edge-disjoint decomposition ofK
n (the complete undirected graph onn vertices) with vertex setS, into copies ofK
4–e, the graph on four vertices with five edges. It is well-known [1] thatK
4–e designs of ordern exist for alln 0 or 1 (mod 5),n 6, and that if (S, B) is aK
4–e design of ordern then |B| =n(n – 1)/10.Asimple covering ofK
n with copies ofK
4–e is a pair (S, C) whereS is the vertex set ofK
n andC is a collection of edge-disjoint copies ofK
4–e which partitionE(Kn)P, for some
. Asimple minimum covering ofK
n (SMCK
n) with copies ofK
4–e is a simple covering whereP consists of as few edges as possible. The collection of edgesP is called thepadding. Thus aK
4–e design of ordern isSMCK
n with empty padding.We show that forn 3 or 8 (mod 10),n 8, the padding ofSMCK
n consists of two edges and that forn 2, 4, 7 or 9 (mod 10),n 9, the padding consists of four edges. In each case, the padding may be any of the simple graphs with two or four edges respectively. The smaller cases need separate treatment:SMCK
5 has four possible paddings of five edges each,SMCK
4 has two possible paddings of four edges each andSMCK
7 has eight possible paddings of four edges each.The recursive arguments depend on two essential ingredients. One is aK
4–e design of ordern with ahole of sizek. This is a triple (S, H, B) whereB is an edge-disjoint collection of copies ofK
4–e which partition the edge set ofK
n\Kk, whereS is the vertex set ofK
n, and
is the vertex set ofK
k. The other essential is acommutative quasigroup with holes. Here we letX be a set of size 2n 6, and letX = {x
1, x2, ..., xn} be a partition ofX into 2-element subsets, calledholes of size two. Then a commutative quasigroup with holesX is a commutative quasigroup (X, ) such that for each holex
i X, (xi, ) is a subquasigroup. Such quasigroups exist for every even order 2n 6 [4]. 相似文献
78.
LUDVÍK BENEŠ KLÁRA MELÁNOVÁ JAN SVOBODA VÍTĚZSLAV ZIMA 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):289-293
Intercalates of o-, m-, and p-toluidine into α-Zr(HPO4)2 · H2O were prepared and characterized by powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. As follows from IR, toludine molecules are protonated in the interlayer space. Toluidine molecules are arranged in a bimolecular way in the intercalates containing more than 1.5 toluidine molecules per Zr atom. On the other hand, a monolayer of the toluidine molecules is supposed in the intercalates with less than one toluidine molecule per Zr atom. 相似文献
79.
Biomolecular homochirality, the origin of which is still a puzzle, has challenged scientists to design chemical systems that provide chiral molecules through absolute asymmetric synthesis and to amplify a small stereochemical bias in such systems. The photoresolution of the enantiomers of helical-shaped, sterically overcrowded alkene 1 with circularly polarized light and the transduction of the stereochemical information by triggering the helical arrangement of a large collection of achiral molecules in a twisted nematic liquid crystalline phase (2) are examples of control and amplification of chirality. 相似文献
80.
Flow injection is used for the determination of pH over a wide range. Using an appropriate combination of pH-indicating dyes, plots of absorbance vs. pH are linear in the range pH < 1–8 for static measurements and pH 3.6–6.8 in the flow-injection experiment. In the current configuration, the flow-injection method has the capability of measuring approximately 100 samples h?1 with a precision and accuracy of ±0.2 pH. The reasons for the linear calibration graphs, effects of ionic strength and day to day reproducibility are presented together with results for lake-water samples. 相似文献