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Simulation of electron bunch generation by an ultrashort-pulse high-intensity laser-driven wakefield
M. Yamagiwa S. V. Bulanov T. Zh. Esirkepov J. Koga M. Kando Y. Ueshima K. Saito D. Wakabayashi 《Laser Physics》2006,16(2):252-258
Electron acceleration due to a wakefield excited by a ultrashort-pulse intense laser propagating through a finite-length underdense plasma layer is studied by two-dimensional particle-in-cell simulation. The electron energy distribution is analyzed for moderate to high intensity. For the electron density, where the pulse length is almost half of the plasma wavelength, dramatic changes of the density structure occur with cavity and bunch formation with an increase in the laser intensity, also leading to the appearance of a fast electron component well confined in phase space. The analytical form of the fast electron energy spectrum is also presented. 相似文献
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Masaharu Tsuji Chikashi Yamagiwa Minoru Endoh Yukio Nishimura 《Chemical physics letters》1980,73(3):407-412
The extensive bands observed from the helium afterglow reaction of SO2 in the 250–540 nm region are assigned to the new SO+(A2Π-X2Πr) system produced from the He+/SO2 dissociative charge-transfer reaction at thermal energy. They had been erroneously interpreted as the SO+2 (C?-X?) system produced from He(23S)/SO2 Penning ionization. The spectroscopic constants for the SO+A2Π) and SO+(X2Πr) states were determined. 相似文献
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Sugita M Yamaguchi A Yamagiwa N Handa S Matsunaga S Shibasaki M 《Organic letters》2005,7(23):5339-5342
[reaction, structure: see text] Chiral Y{N(SiMe3)2}3/linked-BINOL catalyst generated Y-enolate in situ from various hydroxyketones (R2 = aryl, heteroaryl). Beta-amino-alpha-hydroxy ketones (R1 = aryl, heteroaryl, alkenyl) were obtained syn-selectively (up to 96/4) in high ee (up to 98%) and good yield (up to 98% yield). 相似文献
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Y Matsumoto R Tsuzuki A Matsuhisa N Masuda Y Yamagiwa I Yanagisawa T Shibanuma H Nohira 《Chemical & pharmaceutical bulletin》1999,47(7):971-979
Three new series of analogues related to 3,4-dihydro-2H-1,4-benzoxazine derivative 1a were synthesized and evaluated for their potassium channel activating activity. In the first series I, where the 6,7-positions were disubstituted, it was found that an electron-withdrawing substituent was preferable at the 6 position, but either an electron-withdrawing or releasing substituent without bulkiness was tolerated at the 7 position. In the second series II, where several heterocycles were introduced into the 6,7-positions, the oxadiazole derivative 6 showed more potent activity than cromakalim. In the third series III, where the benzene ring was replaced by a pyridine ring, borane complex 16 had equivalent activity to cromakalim. Especially, compound 6 showed a potent hypotensive effect with a long duration of action in the spontaneous hypertensive rat and had a lesser increasing effect on intracranial pressure in dogs than 1a and levcromakalim, showing a good profile as an antihypertensive agent. 相似文献
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Yamagiwa N Qin H Matsunaga S Shibasaki M 《Journal of the American Chemical Society》2005,127(38):13419-13427
The full details of a catalytic asymmetric aza-Michael reaction of methoxylamine promoted by rare earth-alkali metal heterobimetallic complexes are described, demonstrating the effectiveness of Lewis acid-Lewis acid cooperative catalysis. First, enones were used as substrates, and the 1,4-adducts were obtained in good yield (57-98%) and high ee (81-96%). Catalyst loading was successfully reduced to 0.3-3 mol % with enones. To broaden the substrate scope of the reaction to carboxylic acid derivatives, alpha,beta-unsaturated N-acylpyrroles were used as monodentate, carboxylic acid derivatives. With beta-alkyl-substituted N-acylpyrroles, the reaction proceeded smoothly and the products were obtained in high yield and good ee. Transformation of the 1,4-adducts from enones and alpha,beta-unsaturated N-acylpyrroles afforded corresponding chiral aziridines and beta-amino acids. Detailed mechanistic studies, including kinetics, NMR analysis, nonlinear effects, and rare earth metal effects, are also described. The Lewis acid-Lewis acid cooperative mechanism, including the substrate coordination mode, is discussed in detail. 相似文献
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Qin H Yamagiwa N Matsunaga S Shibasaki M 《Journal of the American Chemical Society》2006,128(5):1611-1614
A Bi(OTf)(3)/Cu(CH(3)CN)(4)PF(6) system efficiently promoted intermolecular 1:1 hydroamination of 1,3-dienes with various carbamates, sulfonamides, and carboxamides to afford allylic amines in good yield (up to 96%). Reaction proceeded with 0.5-10 mol % catalyst loading at 25-100 degrees C (generally at 50 degrees C) in 1,4-dioxane within 24 h. The Bi(OTf)(3)/Cu(CH(3)CN)(4)PF(6) system constitutes a new entry into series of intermolecular hydroamination catalysis. Mechanistic studies and the postulated reaction mechanism are also discussed. 相似文献
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M. Kando S. Masuda A. Zhidkov A. Yamazaki H. Kotaki S. Kondo T. Homma S. Kanazawa K. Nakajima L. -M. Chen J. Ma Y. Hayashi M. Mori H. Kiriyama Y. Akahane N. Inoue H. Ueda Y. Nakai K. Tsuji Y. Yamamoto J. Koga T. Hosokai K. Kinoshita A. Maekawa M. Uesaka S. V. Bulanov T. Zh. Esirkepov M. Yamagiwa T. Kimura K. Yamakawa T. Tajima 《Laser Physics》2006,16(4):576-580
We present the results of electron generation experiments conducted at the Advanced Photon Research Center, Japan Atomic Energy Research Institute, using 23-fs relativistically intense 20-TW tightly focused laser pulses with underdense plasma. We observed electron energies up to 40 MeV characterized by a two-temperature Maxwell distribution. With the help of particle-in-cell simulations, we found that these are due to different plasma wave-breaking processes. A charge of 5 nC/shot was obtained at a small solid angle, which corresponds to high peak current generation. 相似文献