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51.
Dmitri V. Zagorevskii Yurii S. Nekrasov John L. Holmes 《Journal of the American Society for Mass Spectrometry》1993,4(3):216-222
The behavior of some substituted cyclopentadienylmanganese ions has been studied by tandem mass spectrometry. This metastable ion study showed that only C5H5Mn+ and (C5H4CN)Mn+ ions retain their nido-cluster structure (1), which is characterized by a simple metal-ligand bond cleavage. Other substituted ions, RXC5H4Mn+, rearrange to a different extent, depending on the nature of the substituent. The first rearrangement step is R radical migration to the central metal atom, leading to RMnC5H4X+-type ions (2). These ions decompose by elimination of X (for X=CO) or with formation of RMnX+, but further rearrangements can also occur. These are the reverse migration of R from the metal atom to the π-ligand (for R=H, Ph) and cyclopentadienyl ring expansion (for X=CH2). Collisional activation mass spectra contained an Mn+ ion peak, which can indicate the existence of stable type 1 structures for most cyclopentadienylmanganese ions. Carboxyl and hydroxymethyl derivatives exist, presumably as ions of type 2. The neutralization-reionization mass spectra of RXC5H4Mn+ ions are also discussed. 相似文献
52.
Yurii M. Ostanevich 《Macromolecular Symposia》1988,15(1):91-103
The operation principles, constructions, advantages and shortcomings of the known Time-of-Flight Small-Angle Neutron Scattering (TOF SANS) spectrometers built up on pulsed neutron sources are reviewed. The most important characteristics of TOF SANS apparatuses are rather a high luminosity and the possibility of measurement in an extremely wide range of the scattering vector at a single exposure. This is achieved by simultaneous employment of the white beam, TOF technique for Λ-scan and the commonly known θ-scan. However, the electronic equipment, data-matching programs and the measurement procedure, necessary for accurate normalization of experimental data and their transformation into absolute cross-section scale - they all become more complex as compared with those for SANS apparatuses operating on steady-state neutron sources, where only θ -scan is used. 相似文献
53.
54.
55.
The mechanisms responsible for enhanced transmission of electromagnetic wave through an array of subwavelength slits in a metallic film are analyzed. Theoretical model of the enhanced transmission which takes into account the penetration of electromagnetic field into real metal is developed. Semi-analytical model based on Fabry–Perot formula is considered. Comparison of theoretical model, semi-analytical model and results of numerical simulation of Maxwell equations in time-dependent form (FDTD method) for silver with various geometric parameters is presented. The roles of surface plasmons and plasmon localized along slits are studied. 相似文献
56.
57.
D. V. Lebedev E. M. Ivan’kova V. A. Marikhin L. P. Myasnikova E. I. Radovanova Yu. M. Boiko M. V. Shtil’man 《Physics of the Solid State》2014,56(6):1249-1255
A comparative investigation of the surface structure of ultrahigh molecular weight polyethylene film filaments obtained with different draw ratios from xerogels prepared from 1.5 wt % polymer solutions in decaline and mineral oil has been performed using a SUPRA-55V scanning electron microscope and a nanoluminograph for recording thermoluminescence of ultrathin near-surface layers of solids. It has been found that, with an increase in the draw ratio, the luminescence intensity decreases, and the peaks responsible for the segmental mobility are shifted toward higher temperatures. It has been assumed that this is associated with the improvement of the structure of near-surface layers of the polymer (with a decrease in the number of microcavities and segments of molecules with a high degree of coiling). It has also been revealed that the peaks observed in glow curves of the oriented gel samples from polymer solutions in decaline are shifted more significantly than those of the gel samples from polymer solutions in mineral oil, and the extremely oriented films are characterized by a large discretization of kinetic units of motion. 相似文献
58.
59.
The universal enveloping C
*-algebra A
of twisted canonical commutation relations is considered. It is shown that, for any (–1,1), the C
*-algebra A
is isomorphic to the C
*-algebra A
0 generated by partial isometries t
i
,t
i
*,i=1,¨,d satisfying the relations
t
i
*
t
j
=
ij
(1–
k<i
t
k
t
k
*), t
j
t
i
=0, ij
and it is proved that the Fock representation of A
is faithful. 相似文献
60.
We have developed an optical stack of holographically formed polymer dispersed liquid-crystal (H-PDLC) devices that is fully operational with nonpolarized light sources. The device consists of two H-PDLC transmission gratings separated by a passive polarization rotator that can output a diffracted s-polarized, p-polarized, or s- and p-polarized beam simultaneously. 相似文献