We present analytical studies of electron acceleration in the low-density preplasma of a thin solid target byan intense femtosecond laser pulse.Electrons in the preplasma are trapped and accelerated by the ponderomoti...We present analytical studies of electron acceleration in the low-density preplasma of a thin solid target byan intense femtosecond laser pulse.Electrons in the preplasma are trapped and accelerated by the ponderomotive forceas well as the wake field.Two-dimensional particle-in-cell simulations show that when the laser pulse is stopped by thetarget,electrons trapped in the laser pules can be extracted and move forward inertially.The energetic electron bunchin the bubble is unaffected by the reflected pulse and passes through the target with small energy spread and emittance.There is an optimal preplasma density for the generation of the monoenergetic electron bunch if a laser pulse is given.The maximum electron energy is inverse proportion to the preplasma density.展开更多
To gain insight into the attachment of =Si^＋ （SC） ion （regarded as guest） to the lowest generation, NH2-terminated poly（amidoamine） （PAMAM） dendrimers （regarded as host） in the liquid phase, density functio...To gain insight into the attachment of =Si^＋ （SC） ion （regarded as guest） to the lowest generation, NH2-terminated poly（amidoamine） （PAMAM） dendrimers （regarded as host） in the liquid phase, density functional theory is used to investigate the structures and energetics of the host-guest complex. The effect of solvent on the structures and energetics is also investigated. Various initial configurations of the ion bound to PAMAM are tested, and two stable conformers are found, i.e, types A （=Si^＋ is bound to the amine site） and C （=Si^＋ is bound to the amide site）. Types A and C are the most stable due to the chemical bond formations of Si-N° （amine nitrogen atoms） and Si-O, respectively. The IR spectra for the lowest energy conformers are thoroughly analyzed and compared with the available experimental data.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.10875015,10834008,10963002the 973 Program under Grant No.2006CB806004Educational Commission of Jiangxi Province of China under Grant No.GJJ10052
文摘We present analytical studies of electron acceleration in the low-density preplasma of a thin solid target byan intense femtosecond laser pulse.Electrons in the preplasma are trapped and accelerated by the ponderomotive forceas well as the wake field.Two-dimensional particle-in-cell simulations show that when the laser pulse is stopped by thetarget,electrons trapped in the laser pules can be extracted and move forward inertially.The energetic electron bunchin the bubble is unaffected by the reflected pulse and passes through the target with small energy spread and emittance.There is an optimal preplasma density for the generation of the monoenergetic electron bunch if a laser pulse is given.The maximum electron energy is inverse proportion to the preplasma density.
文摘To gain insight into the attachment of =Si^＋ （SC） ion （regarded as guest） to the lowest generation, NH2-terminated poly（amidoamine） （PAMAM） dendrimers （regarded as host） in the liquid phase, density functional theory is used to investigate the structures and energetics of the host-guest complex. The effect of solvent on the structures and energetics is also investigated. Various initial configurations of the ion bound to PAMAM are tested, and two stable conformers are found, i.e, types A （=Si^＋ is bound to the amine site） and C （=Si^＋ is bound to the amide site）. Types A and C are the most stable due to the chemical bond formations of Si-N° （amine nitrogen atoms） and Si-O, respectively. The IR spectra for the lowest energy conformers are thoroughly analyzed and compared with the available experimental data.
