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121.
122.
Femtosecond high-order harmonic transient absorption spectroscopy is used to resolve the complete |j,m quantum state distribution of Xe+ produced by optical strong-field ionization of Xe atoms at 800 nm. Probing at the Xe N4/5 edge yields a population distribution rhoj,|m| of rho3/2,1/2ratiorho1/2,1/2ratiorho3/2,3/2=75+/-6 :12+/-3 :13+/-6%. The result is compared to a tunnel ionization calculation with the inclusion of spin-orbit coupling, revealing nonadiabatic ionization behavior. The sub-50-fs time resolution paves the way for tabletop extreme ultraviolet absorption probing of ultrafast dynamics. 相似文献
123.
The reaction of [CpFe(CO)2]2 with NH4Se2P(OR)2 yields a novel reagent Cp(CO)2FeP(Se)(OR)2, which has demonstrated coordination properties at the Se center to form heterometallic clusters as well as reactivity at the Se site toward C-based electrophiles. 相似文献
124.
2,3-Diarylquinoxaline directed mono ortho-aroylation protocol has been developed using aromatic aldehydes or alkybenzenes as aroyl surrogates. Out of the four available ortho sp2 C–H bonds in the two aryl rings of 2,3-diarylquinoxaline one of the C–H bond is selectively ortho-aroylated. The reaction proceeds via the aroyl radical path in the case of aromatic aldehydes while the alkylbenzenes follow either an aroyl radical or a benzyl radical path. Varieties of functional groups present as substituents in 2,3-diarylquinoxalines, aromatic aldehydes and alkylbenzenes are tolerated under the present reaction conditions. 相似文献
125.
Sougata Santra Shubhanjan MitraAvik Kumar Bagdi Adinath MajeeAlakananda Hajra 《Tetrahedron letters》2014
An efficient, one-pot, three-component domino strategy has been demonstrated for the synthesis of imidazo[1,2-a]pyridines using a catalytic amount of Fe(III) chloride in high yields in air. A library of imidazo[1,2-a]pyridines was synthesized by the reaction of easily available aldehydes and 2-aminopyridines in a mixture of nitroalkane and DMF (2:1). This transformation presumably occurs by a sequential aza-Henry reaction/cyclization/denitration. The use of readily available chemicals as starting materials, inexpensive metal catalyst, aerobic reaction conditions, tolerance of a wide range of functional groups, and operational simplicity are the notable advantages of this present protocol. 相似文献
126.
H. M. Chawla S. Kumar N. Pant A. Santra K. Sriniwas N. Kumar David StC. Black 《Journal of inclusion phenomena and macrocyclic chemistry》2011,71(1-2):169-178
A series of deep cavity diphenyl imidazolyl calix[n]arenes (4, 6, 8) have been obtained from readily available starting materials through a five step synthetic methodology involving appropriate alkylation of lower rim of preformed calixarene, formylation of the upper rim and subsequent condensation with aryl diketones in the presence of ammonium acetate and glacial acetic acid. Optimized reaction conditions for obtaining the titled derivatives in their cone configuration and their characterization by spectroscopic methods (IR, UV, NMR and FAB mass) have been delineated. The synthesized imidazolyl calixarenes have preliminarily been examined for selective recognition of monovalent metal ions (Li+, Na+, K+, Cs+, Ag+). 相似文献
127.
128.
In this paper, we report the synthesis and self assembly of various sizes of ZnO nanocrystals. While the crystal structure
and the quantum confinement of nanocrystals were mainly characterized using XRD and UV absorption spectra, the self assembly
and long range ordering were studied using scanning tunneling microscopy after spin casting the nanocrystal film on the highly
oriented pyrolytic graphite surface. We observe self assembly of these nanocrystals over large areas making them ideal candidates
for various potential applications. Further, the electronic structure of the individual dots is obtained from the current–voltage
characteristics of the dots using scanning tunneling spectroscopy and compared with the density of states obtained from the
tight binding calculations. We observe an excellent agreement with the experimentally obtained local density of states and
the theoretically calculated density of states.
We dedicate this work to Professor C. N. R. Rao on the occasion of his 75th birthday. 相似文献
129.
A convenient synthetic strategy for the synthesis of the acidic pentasaccharide repeating unit and its trisaccharide fragment corresponding to the O-antigen of Shigella boydii type 6 has been successfully developed. A stereoselective sequential glycosylation method has been exploited to obtain the target tri- and pentasaccharide derivatives. Most of the synthetic intermediates were solid and prepared in high yields from commercially available reducing sugars following a series of protection–deprotection reactions. A late-stage TEMPO mediated selective oxidation reaction finally resulted in the pentasaccharide containing a glucuronic acid unit. A 2-(4-methoxyphenoxy) ethyl group has been chosen as the anomeric protecting group to provide trisaccharide and pentasaccharide derivatives linked to an ethylene glycol linker. 相似文献
130.
T. Shiroka C. Bucci R. De Renzi F. Galli G. Guidi G. H. Eaton P. J. C. King C. A. Scott K. Träger A. Breitrück M. Diaz Trigo A. Großmann K. Jungmann J. Merkel P. Neumayer I. Reinhard R. Santra L. Willmann V. Meyer E. Roduner R. Scheuermann M. C. Charlton P. Donnelly 《Applied magnetic resonance》2000,19(3-4):471-477
Standard muon spin rotation (μSR) spectroscopy implants 4 MeV spin-polarized positive muons to investigate the bulk properties of matter. Success in producing epithermal muons opens interesting possibilities for studying ultrathin films, interfaces, and even surfaces. At the ISIS Facility, Rutherford Appleton Laboratory (Chilton, UK), we have produced a pulsed ultraslow muon beam (E< 20 eV) and have performed the first μSR experiments. Due to the pulsed feature, the implantation time is automatically determined and, by adjusting the final muon energy between about 8 and 20 eV, depth slicing experiments are possible down to monolayers distances. We describe slicing experiments across a 20 nm copper film on quartz substrate with evidence for a 2 nm copper oxide surface layer. A preliminary experiment on a hexagonal cobalt film suggests the existence of muon precession in the local magnetic field. The results are discussed in relation to the morphological features of the film. 相似文献