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991.
Kamariotis A Boyarkin OV Mercier SR Beck RD Bush MF Williams ER Rizzo TR 《Journal of the American Chemical Society》2006,128(3):905-916
We report here infrared spectra of protonated and lithiated valine with varying degrees of hydration in the gas phase and interpret them with the help of DFT calculations at the B3LYP/6-31++G** level. In both the protonated and lithiated species our results clearly indicate that the solvation process is driven first by solvation of the charge site and subsequently by formation of a second solvation shell. The infrared spectra of Val x Li+ (H2O)4 and Val x H+ (H2O)4 are strikingly similar in the region of the spectrum corresponding to hydrogen-bonded stretches of donor water molecules, suggesting that in both cases similar extended water structures are formed once the charge site is solvated. In the case of the lithiated species, our spectra are consistent with a conformation change of the amino acid backbone from syn to anti accompanied by a change in the lithium binding from a NO coordination to OO coordination configuration upon addition of the third water molecule. This change in the mode of metal ion binding was also observed previously by Williams and Lemoff [J. Am. Soc. Mass Spectrom. 2004, 15, 1014-1024] using blackbody infrared radiative dissociation (BIRD). In contrast to the zwitterion formation inferred from results of the BIRD experiments upon addition of a third water molecule, our spectra, which are a more direct probe of structure, show no evidence for zwitterion formation with the addition of up to four water molecules. 相似文献
992.
Ott S Borgström M Hammarström L Johansson O 《Dalton transactions (Cambridge, England : 2003)》2006,(11):1434-1443
The synthesis, characterization, and photophysical properties of the N6-N5C bichromophoric [(bpy)2Ru(I)Ru(ttpy)][PF6]3 (bpy is 2,2'-bipyridine and ttpy is 4'-p-tolyl-2,2':6',2'-terpyridine) and [(bpy)2Ru(II)Ru(ttpy)][PF6]3 (I and II are bpy-dipyridylbenzene ditopic ligands bridged by an ethynyl and phenyl unit, respectively) complexes are reported together with the model mononuclear complexes [(bpy)2Ru(I)][PF6]2, [(bpy)2Ru(II)][PF6]2, [Ru(VI)(ttpy)][PF6] (VI is 3,5-di(2-pyridyl)-biphenyl) and [Ru(dpb)(ttpy)][PF(6)] (Hdpb is 1,3-di(2-pyridyl)-benzene). The electrochemical data show that there is little ground state electronic communication between the metal centers in the bimetallic complexes. Selective excitation of the N(5)C unit in the bichromophoric systems leads to luminescence typical for a bis-tridentate cyclometallated ruthenium complex and is similar to the [Ru(VI)(ttpy)][PF6] model complex. In contrast, the luminescence from the tris-bidentate N6 unit is efficiently quenched by energy transfer to the N5C unit. The energy transfer rate has been determined by femtosecond pump-probe measurements to 0.7 ps in the ethynyl-linked [(bpy)2Ru(I)Ru(ttpy)][PF6]3 and to 1.5 ps in the phenyl-linked [(bpy)2Ru(II)Ru(ttpy)][PF6]3 (in acetonitrile solution at 298 K), and is inferred to occur via a Dexter mechanism. 相似文献
993.
Ptasińska S Echt O Denifl S Stano M Sulzer P Zappa F Stamatovic A Scheier P Märk TD 《The journal of physical chemistry. A》2006,110(27):8451-8456
We report on attachment of free electrons to fullerenes C(n) (n = 60, 70, 76, 78, 80, 82, 84, 86) and to Sc(3)N@C(80). The attachment cross sections exhibit a strong resonance at 0 eV for all species. The overall shape of the anion yield versus electron energy is quite similar for the higher fullerenes, with a minimum around 1 eV and a maximum which gradually shifts from 6 eV for C(60) to approximately 4 eV for large n. The endohedral Sc(3)N@C(80) exhibits a particularly shallow minimum and a maximum below 4 eV. We model autoionization of the anions with due consideration of the internal energy distributions. The relatively low electron affinity of Sc(3)N@C(80) is reflected in its reduced ion yield at higher attachment energies. 相似文献
994.
S. Eliseev Ch. Böhm D. Beck K. Blaum M. Breitenfeldt V.N. Fedosseev S. George F. Herfurth A. Herlert H.-J. Kluge M. Kowalska D. Lunney S. Naimi D. Neidherr Yu.N. Novikov M. Rosenbusch L. Schweikhard S. Schwarz M. Seliverstov K. Zuber 《Physics letters. [Part B]》2010
The study of nuclear electron capture (EC) offers an exciting alternative for the determination of the neutrino mass. Whereas only tritium and 187Re can be used in the case of β-decay experiments involving the anti-neutrino, a potentially large number of EC-nuclides can be used in experiments involving the monochromatic neutrino. This alternative to β -decay experiments requires an accurate measurement of QEC-values of appropriate candidates. In the present work we initiate a search for such a candidate and determined the QEC-value of the electron capture in 194Hg by direct mass measurements of 194Hg and 194Au. The new QEC-value of 29(4) keV determined by the ISOLTRAP Penning-trap mass spectrometer at ISOLDE/CERN forbids the K-capture for 194Hg. However, it allows a determination of the neutrino mass by a combination of a micro-calorimetric measurement of the de-excitation spectrum from L-capture in 194Hg and a comparable QEC-value remeasurement by high-precision Penning trap mass spectrometry. 相似文献
995.
S. Schumann B. Boillat E. J. Downie P. Aguar-Bartolomé J. Ahrens J. R. M. Annand H. J. Arends R. Beck V. Bekrenev A. Braghieri D. Branford W. J. Briscoe J. W. Brudvik S. Cherepnya R. Codling P. Drexler L. V. Fil’kov D. I. Glazier R. Gregor E. Heid D. Hornidge O. Jahn V. L. Kashevarov R. Kondratiev M. Korolija M. Kotulla D. Krambrich B. Krusche M. Lang V. Lisin K. Livingston S. Lugert I. J. D. MacGregor D. M. Manley M. Martinez-Fabregate J. C. McGeorge D. Mekterovic V. Metag B. M. K. Nefkens A. Nikolaev R. Novotny M. Ostrick R. O. Owens P. Pedroni A. Polonski S. N. Prakhov J. W. Price G. Rosner M. Rost T. Rostomyan D. Sober A. Starostin I. Supek C. M. Tarbert A. Thomas M. Unverzagt Th. Walcher D. P. Watts F. Zehr 《The European Physical Journal A - Hadrons and Nuclei》2010,43(3):269-282
The reaction γp → pπ 0γ′ has been measured with the Crystal Ball/TAPS detectors using the energy-tagged photon beam at the electron accelerator facility MAMI-B. Energy and angular differential cross-sections for the emitted photon γ′ and angular differential cross-sections for the π0 have been determined with high statistics in the energy range of the Δ+ (1232)-resonance. Cross-sections and the ratio of the cross-section to the nonradiative process γp → pπ 0 are compared to theoretical reaction models, having the anomalous magnetic moment κ Δ as free parameter. As the shape of the experimental distributions is not reproduced in detail by the model calculations, currently no extraction of κ Δ is feasible. 相似文献
996.
F. A. Souza N. Carlin C. Beck N. Keeley A. Diaz-Torres R. Liguori Neto C. Siqueira-Mello M. M. de Moura M. G. Munhoz R. A. N. Oliveira M. G. Del Santo A. A. P. Suaide E. M. Szanto A. Szanto de Toledo 《The European Physical Journal A - Hadrons and Nuclei》2010,44(2):181-187
A study of the kinematics of the $ \alpha$ -d coincidences in the 6Li + 59Co system at a bombarding energy of E lab = 29.6 MeV is presented. With exclusive measurements performed over different angular intervals it is possible to identify the respective contributions of the sequential and direct projectile breakup components. The angular distributions of both breakup components are fairly well described by the Continuum-Discretized Coupled-Channels framework (CDCC). Furthermore, a careful analysis of these processes using a semiclassical approach provides information on both their lifetime and their distance of occurrence with respect to the target. Breakup to the low-lying (near-threshold) continuum is delayed, and happens at large internuclear distances. This suggests that the influence of the projectile breakup on the complete fusion process can be related essentially to the direct breakup to the 6Li high-lying continuum spectrum. 相似文献
997.
J. Ahrens S. Altieri J. R. M. Annand H. -J. Arends R. Beck M. A. Blackston C. Bradtke A. Braghieri N. d’Hose H. Dutz A. Fix E. Heid O. Jahn F. Klein R. Kondratiev M. Lang V. Lisin M. Martinez-Fabregate J. C. McGeorge W. Meyer A. Panzeri P. Pedroni T. Pinelli D. Protopopescu G. Reicherz Ch. Rohlof G. Rosner T. Rostomyan D. Ryckbosch M. Schwamb G. Tamas A. Thomas H. R. Weller 《The European Physical Journal A - Hadrons and Nuclei》2010,44(2):189-201
998.
The side class structure of a perfect 1-error correcting binary code (hereafter referred to as a perfect code) C describes the linear relations between the coset representatives of the kernel of C. Two perfect codes C and C′ are linearly equivalent if there exists a non-singular matrix A such that AC = C′ where C and C′ are matrices with the code words of C and C′ as columns. Hessler proved that the perfect codes C and C′ are linearly equivalent if and only if they have isomorphic side class structures. The aim of this paper is to describe
all side class structures. It is shown that the transpose of any side class structure is the dual of a subspace of the kernel
of some perfect code and vice versa; any dual of a subspace of a kernel of some perfect code is the transpose of the side
class structure of some perfect code. The conclusion is that for classification purposes of perfect codes it is sufficient
to find the family of all kernels of perfect codes. 相似文献
999.
1000.
Olof Heden 《Designs, Codes and Cryptography》2008,46(1):45-56
Let p be a prime number and assume p ≥ 5. We will use a result of L. Redéi to prove, that every perfect 1-error correcting code C of length p + 1 over an alphabet of cardinality p, such that C has a rank equal to p and a kernel of dimension p − 2, will be equivalent to some Hamming code H. Further, C can be obtained from H, by the permutation of the symbols, in just one coordinate position.
相似文献