首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9篇
  免费   4篇
  国内免费   11篇
化学   7篇
物理学   17篇
  2021年   1篇
  2014年   1篇
  2013年   2篇
  2012年   1篇
  2010年   2篇
  2007年   4篇
  2006年   4篇
  2005年   2篇
  2003年   1篇
  1998年   1篇
  1994年   1篇
  1990年   1篇
  1983年   1篇
  1982年   1篇
  1977年   1篇
排序方式: 共有24条查询结果,搜索用时 31 毫秒
1.
在样品池条件下,用脉冲激光670.8 nm线激发Li原子基态至2P态,测量了的反应碰撞能量转移截面。池温保持在888 K,Li原子密度为10~(13)cm~(-3)量级,而H_2气压控制在60~300 Pa之间,测量时间分辨荧光光谱,它由两部分组成,在脉冲激光激发的瞬间(不超过10 ns),荧光迅速增强至最大值;激发结束后,荧光强度按指数衰减,由衰减曲线得到2P态原子在不同H_2气压下的有效寿命。根据Stern-Volmer方程,有效寿命与H_2气压成线性关系,由该直线的斜率给出了总的猝灭截面(25.1±4.0)×10~(-16)cm~2,而从直线的截距得到辐射寿命为(270±54)ns。总的猝灭截面是反应与非反应碰撞截面之和,由在不同H_2气压下记录的瞬态(10 ns)荧光快速增强信号得到反应截面为(0.2±0.1)×10~(-16)cm~2,虽只占总猝灭截面的1/125,但它在Li(2P)+H_2的碰撞传能中所起的作用是不能略去的。  相似文献   
2.
用基于密度泛函理论的局域密度近似平面波超软赝势方法,计算了H2O分子在LiH表面的最佳吸附方式,得到了倾斜吸附的构型,其偏转角为37.85°.由吸附前后的态密度(DOS)图可知,成键主要由LiH的s、p轨道和H2O的sp3轨道杂化而成,成键峰重叠性较强,且峰增宽,有明显的共价成分.其吸附能为-43.2 kJ/mol,为化学吸附.结果显示,H2O分子在LiH表面吸附的吸附性质和构型与实验结果一致,并有形成LiOH的趋势.  相似文献   
3.
Summary Meldrum's acid (1) reacts with isothiocyanates and LiH as base, yielding after alkylation the ketene-S,N-acetales3,4 and5. Protonation of the lithium-thiolate2 gives the thioamides7 with tautomers8, which can be methylated with diazomethane to9. From1 and7 it is possible to obtain the amides12.2 reacts with -bromo-carboxylic esters and bromo-acetone, yielding thiazolidones15,16 and thiazolines18.
  相似文献   
4.
利用SAC(Symmetry-Adapted Cluster)/SAC-CI(Configuration Interaction)理论中的SAC-CI-NV(Non-variational)and SAC-CI-V(Variational)方法,以及6-311 g**基组对LiH分子的基态(X1∑ )和A1∑ 、B1∏激发态的平衡结构以及性质进行了研究计算.两种方法对LiH分子的三个态进行处理,并将优化结果与现有实验值进行了比较,结果显示,理论计算值都与实验值符合较好.同时利用SAC/SAC-CI方法中的AllProperties关键字对我们所关心的LiH分子的基态(X1∑ )和A1∑ 、B1∏激发态进行了计算,并给出各个态在其平衡点位置处的偶极矩、振子强度和抗磁化率等一些性质参数,对以后的实验作理论参考.  相似文献   
5.
利用基于密度泛函理论的第一性原理平面波超软赝势方法,计算了LiH在零温零压下的晶格常数、体弹模量,计算结果与实验值和其他理论计算值符合得较好.通过准谐德拜模型计算了LiH在压强为0-80GPa、温度为0-2000K范围内,体积膨胀率、热涨系数、德拜温度及定容热容随压强和温度的变化关系.最后,以代数方法(AM)和势能变分法(PVM)为基础,运用统计热力学理论计算了LiH分子内部运动对体系热力学性质的影响.  相似文献   
6.
A series of diamond crystals doped with hydrogen is successfully synthesized using LiH as the hydrogen source in a catalyst-carbon system at a pressure of 6.0 GPa and temperature ranging from 1255 C to 1350 C.It is shown that the high temperature plays a key role in the incorporation of hydrogen atoms during diamond crystallization.Fourier transform infrared micro-spectroscopy reveals that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp 3-CH 2-symmetric(2850 cm-1) and sp 3 CH 2-antisymmetric vibrations(2920 cm-1).The intensities of these peaks increase gradually with an increase in the content of the hydrogen source in the catalyst.The incorporation of hydrogen impurity leads to a significant shift towards higher frequencies of the Raman peak from 1332.06 cm-1 to 1333.05 cm-1 and gives rise to some compressive stress in the diamond crystal lattice.Furthermore,hydrogen to carbon bonds are evident in the annealed diamond,indicating that the bonds that remain throughout the annealing process and the vibration frequencies centred at 2850 and 2920 cm-1 have no observable shift.Therefore,we suggest that the sp 3 C-H bond is rather stable in diamond crystals.  相似文献   
7.
低碰撞能下Ne原子对LiH分子转动猝灭的研究   总被引:1,自引:0,他引:1  
用密耦方法首次研究了Ne原子和LiH分子低能碰撞下的转动猝灭过程.在碰撞能低于10-4cm-1时,弹性截面趋于常数值,非弹性截面随碰撞速度减小线性增加,遵循Wigner定则预言的趋势.对于一个给定的能量,总的猝灭截面是随着初始j的增加而减少的.当能量在0.01~100 cm-1范围内,弹性和非弹性截面均比其它的体系表现出更复杂的振荡行为,这主要是由于体系具有强的各向异性以及它们具有两个吸引阱而造成的.计算表明,在零温极限下,猝灭速率系数达到10-11cm3s-1数量级.当j=7速率系数出现反转结构.  相似文献   
8.
Summary Electron correlation in the H2, LiH and BH molecules has been analyzed in terms of the statistical correlation coefficients introduced by Kutzelnigg, Del Re, and Berthier. Angular, radial (in-out), longitudinal (left-right) and transverse correlation coefficients have been evaluated from both self-consistent-field (SCF) and configuration interaction (CI) wave functions. It has been found that these coefficients reflect fairly well the correlation behavior in the molecular system. The lack of spherical symmetry in molecular densities adds new features to these correlation coefficients and this information can be useful for the study of electronic structure in molecules. The correlation hole function, Fermi and Coulomb holes in these systems have also been calculated and discussed.Dedicated to Professor Werner Kutzelnigg on the occasion of his sixtieth birthday  相似文献   
9.
He-LiH体系转动非弹性碰撞的理论研究   总被引:8,自引:3,他引:5  
在单双迭代耦合簇CCSD(T)势能面的基础上,运用密耦方法讨论了He-LiH体系的转动非弹性碰撞.计算结果表明,对LiH分子j=0→j′跃迁,跃迁截面主要由各向异性的短程相互作用和长程的“软”排斥共同作用的结果,未见明显的长程吸引势贡献.态-态跃迁总截面表现出振荡结构,长程“软”排斥分波只对j=0向j′=1、2、3的跃迁总截面有较大贡献,而j′≥ 4跃迁的积分截面则几乎由各向异性的短程部分贡献.  相似文献   
10.
The molecules LinHn, NanHn, LinFn, n=1,..., 4, and NaF and Na2F2 are investigated by means of extended basis set SCF and CEPA-PNO computations. In analogy to the D 2h structure of dimers, it is found that trimers have a planar cyclic D 3h equilibrium geometry. For the tetramer of LiH and NaH, the D 4h structure has about the same energy as the 3-dimensional T d structure, whereas the latter is definitely favoured for Li4F4. Correlation effects are investigated for the oligomerization of LiH and the dimerization of LiF. The effect of electron correlation on corresponding E turns out to be small (<4 kJ/mol), except for the case that the T d tetramer is involved which has a rather large correlation energy.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号