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排序方式: 共有680条查询结果,搜索用时 15 毫秒
41.
建立了一个反映高重复率脉冲放电激励的Sr离子自终止激光和复合激光交替振荡的动力学模型,得到了与实测光电脉冲波形相一致的模拟结果.给出了He-Sr放电等离子中长寿命粒子、激光上下能级粒子数密度和电子温度随时间的演化过程.分析了两种激光交替振荡的发射过程、脉冲宽度特性和粒子数反转机理,认为在放电早期和余辉期电子温度的急剧升高和降低是Sr离子自终止和复合激光实现交替振荡的关键所在.
关键词:
自终止激光
复合激光
交替振荡
动力学模型 相似文献
42.
A. Surzhykov U. D. Jentschura T. Stöhlker S. Fritzsche 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):27-36
We apply the density matrix theory to re-investigate the radiative
electron capture into heavy ions with one valence electron. Attention
has been paid particularly to the magnetic sublevel population of the
residual ions, as described in terms of alignment parameters. Simple
method, based on an independent particle model, which takes
into account the Pauli principle, is proposed for evaluating the
alignment of the excited ionic states. By making use of this method,
detailed calculations are performed for electron capture into (initially) hydrogen-like and lithium-like europium, gold and
uranium ions, and are compared with the results of the multiconfiguration Dirac-Fock approach.As seen from the calculations
and from the comparison with available experimental results, the independent particle model provides a good estimate for the
alignment parameters of few-electron heavy ions. Therefore, our simple model may help to understand the basic properties of
the X-ray emission from heavy, few-electron ions without the need for invoking sophisticated MCDF calculations. 相似文献
43.
The distinctive features of the formation of the catalyticity of materials with respect to atom recombination on the material surface are investigated for mixtures of different high-temperature gases under conditions of hypersonic atmospheric flight or bench setups. It is shown that in general the catalyticity constants (heterogenous recombination probabilities) of individual components determined experimentally in dissociated flows of “pure” gases are improperly used for calculating the heat fluxes to material surfaces in multicomponent gas flows, owing to differences in the occupation of the surface by atoms in pure gases and mixtures. This effect must be taken into account in interpreting the experimental data which so far have been the only source of information on material catalyticity in gas mixtures. Otherwise, the results of calculations of the heat transfer to hypersonic flight vehicles could turn out to be invalid. Examples of the possible effect of ignoring this factor on the calculated heat fluxes are presented. 相似文献
44.
F.-J. Zhang Z. Xu Y.-G. Lv J.-C. Zhang S. L. Zhao J.-Z. Huang Y. Wang G.-C. Yuan D.-W. Zhao X.-R. Xu 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):245-248
The organic-inorganic combined structural device (ITO/PVK:Eu/ZnS/Al) is
fabricated based on layered optimization scheme. II–VI semiconductor
material ZnS is acted as an electron function (transporting and
acceleration) layer. The hot electrons which have been accelerated in the
ZnS layer directly impact excitation europium ions through resonant energy
transfer and then recombine with injected holes to form excitons in PVK or
EuTTA2(N-HPA)Phen. Europium (Eu) ions may also be excited by
intramolecular energy transfer from ligands. There are two kinds of
excitation mechanisms: impacted excitation and injected recombination for
the combined structural device. The electroluminescence (EL) intensity of
the combined structural device is strongly improved and reaches up to
381 cd/m2 at 20 V compared with the pure organic structural device. It
may be an effective method to improve the EL intensity of the lanthanide
complex by using electric characteristics of inorganic semiconductor
materials. 相似文献
45.
Andrew C. Benniston Dr. Graeme Copley Dr. Helge Lemmetyinen Dr. Nikolai V. Tkachenko Dr. 《Chemphyschem》2010,11(8):1685-1692
Two series of geometrically‐related dyads are discussed based on the difluoroborondipyrromethene (Bodipy) unit, and incorporating covalently attached hydroquinone/quinone groups. These units are anchored directly, or via a phenylene spacer, to the Bodipy core at the meso position in one series ( BD‐MHQ , BD‐MQ , BD‐MPHQ , BD‐MPQ ), but for the second series the attachment site is the 2‐position ( BD‐SHQ , BD‐SQ , BD‐SPHQ , BD‐SPQ ). The compounds show various levels of fluorescence depending on the oxidation state of the appended group and the substitution pattern. In non‐polar solvents such as toluene, diethyl ether and dichlorobenzene, the S1 state deactivation of the Bodipy unit in BD‐SPQ and BD‐MPQ is dominated by 1, 3exciplex formation, which has not been reported for Bodipy derivatives so far. In the latter molecule, the decay of the exciplex is divided between population of the Bodipy triplet state (13 %–21 %) and ground state reformation. This partitioning is not seen for the side‐on substituted derivative, BD‐SPQ , and only ground state reformation is observed following decay of the exciplex. This difference in behavior is explained by the radical‐pair inter‐system‐crossing mechanism, which more effectively operates in BD‐MPQ because of the orthogonality of the donor‐acceptor units. In the more polar solvent CH3CN all the quinone derivatives show fast formation of the charge‐separated state (kCS) followed by slower charge recombination (kCR). The ratio kCS/kCR≤80. 相似文献
46.
小批量制备质谱纯鲨鱼肝铁蛋白(Liver Ferritin of Sphyrna zygaena,SZLF)。在弱酸介质(pH1.0)中,天然电泳结果显示,SZLF蛋白质亚基20 min后开始解离。选用透射电子显微镜跟踪SZLF亚基解离与重组装全过程和蛋白壳与铁核尺寸变化,发现SZLF在亚基酸解离过程中,随着pH值的降低,铁核和蛋白壳的尺寸呈现相同的变化趋势,这种变化趋势可能与铁核内层铁的释放和蛋白壳的解离与去折叠有关。SZLF蛋白壳的重组装过程则是一个快速过程,并且是由松散熔球态向紧密态转变的过程。SZLF由单类型亚基组成,而马脾铁蛋白(Horse Spleen Ferritin,HSF)由H和L两种亚基类型组成。在基质pH3.0条件和激光辅助下,混合HSF和SZLF仍然可释放各自的亚基且形成准亚基离子,供基质辅助激光解析电离飞行时间质谱分析,说明此时SZLF的亚基间相互作用强度减弱但并没有去折叠。TEM技术在铁蛋白解离和重组装过程中的应用,为进一步研究铁蛋白纳米包装的过程和机理提供新颖的、可行的和更加直观的研究手段。 相似文献
47.
Silicon-rich hydrogenated amorphous silicon nitride (a-SiNx:H) films were grown by plasma enhanced chemical vapor deposition (PECVD) with different r=NH3/SiH4 gas flow ratios. The optical absorption characteristics were analyzed by Fourier transform infrared (FTIR) and UV-visible transmittance spectroscopies. The recombination properties were investigated via photoluminescence (PL) measurements. As r was increased from 2 to 9, the PL emission color could be adjusted from red to blue with the emission intensity high enough to be perceived by naked eye at room temperature. The behaviors of the PL peak energy and the PL band broadness with respect to the optical constants were discussed in the frame of electron-phonon coupling and band tail recombination models. A semiquantitative analysis supported the band tail recombination model, where the recombination was found to be favored when the carriers thermalize to an energy level at which the band tail density of states (DOS) reduces to some fraction of the relevant band edge DOS. For the PL efficiency comparison of the samples with different nitrogen contents, the PL intensity was corrected for the absorbed intensity fraction of the incident PL excitation source. The resulted correlation between the PL efficiency and the subgap absorption tail width further supported the band tail recombination model. 相似文献
48.
R.K. Bhan Raghvendra Sahai Saxena N.K. Saini L. Sareen R. Pal R.K. Sharma 《Infrared Physics & Technology》2011,54(5):379-381
Hg1−xCdxTe Metal–Insulator–Semiconductor (MIS) capacitors were studied both experimentally and theoretically to investigate the capacitance contributions due to band-to-band (btb) tunnelling and generation–recombination (gr) of carriers to inversion layer capacitance. A good fit to the data has been obtained by including the btb contributions rather than gr contributions. 相似文献
49.
Degrading the recombination activities of grain boundaries (GBs) is essential to improve the efficiency of multi‐crystalline silicon (mc‐Si) based solar cells. We apply the deep level transient spectroscopy technique to detect interface states at Σ3 and Σ9 GBs in mc‐Si. The density of interface states close to midgap is found comparable for both as‐grown GBs. Gettering or hydrogenation leads to shallower states with a smaller capture cross section and lower density. Recombination activity reduction for Σ3 GBs is stronger than for Σ9 GBs especially after hydrogenation. Both the analysis approach and experimental results could be applied for a specific GB engineering of mc‐Si based solar cells. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
50.
Auger processes are investigated for CdS/ZnS core-shell quantum dots. Auger recombination (AR) lifetime and electron relaxation inside the core are computed. Using the effective-mass theory and by solving a three-dimension Schrödinger equation we predict the dependence of Auger relaxation on size of core-shell nanocrystals. We considered in this work different AR processes: the excited electron (EE), excited hole (EH), multiexciton AR type. Likewise, Auger multiexciton recombination rates are predicted for biexciton. Our results show that biexciton AR type is more efficient than the other AR process (excited electron (EE) and excited hole (EH)). We also found that electron Auger relaxation P→S is very efficient in core-shell nanostructures. 相似文献