排序方式: 共有21条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
乾根—别卡曾经分析过原子晶体中的极化子问题。文中指出,其中弹性形变的考虑是不正确的,而且“绝热型”的极化子,在例如Ge,Si等原子晶体中存在的可能性是十分微小的。以微扰论为基础的计算证明,电子引起的局部体积变化发生在半径≈λ的范围内,λ是以声速运动的电子的德布罗意波长。局部体变的数值等於E/(α+4/3μ)(E为形变势常数,α和μ分别为体变和切变模量)。局部体变还在样品中引起一个均匀的形变,两者合起来使样品体积改变E/α。具体的分析证明,在类氢的杂质能级中的电子使样品体积产生同样的体积变化。这个效应是相当大的;例如,在Ge和Si这样的晶体中,效应甚至可以舆实验所观测到Ⅲ,Ⅴ族杂质原子的体积效应相比拟。导带中低速电子能量的改变约等於(电子质量/原胞质量)(E/(kΘD))E;在Ge晶体中,如果E=1—10电子伏,能量改变是0.001—0.1电子伏。相应的有效质量改变是1/1000—1/10电子质量。在类氢杂质能级中,电子能量改变远比上值为小;理论上电子—晶格互作用有着可能致使类氢能级自发电离。 相似文献
5.
This study directly analyzes Si in airborne particulate matter by laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) as well as X-ray fluorescence (XRF). 相似文献
6.
本文提出了测试平面衍射光栅的分辨特性的新方法,用干涉法测量光栅衍射的波阵面的相位,得出衍射波阵面的三维波面图,并用所取得的相位数据作傅里叶变换求得其在谱面上的光谱衍射斑——光谱线像的强度分布,并可据此确定半宽度值和分辨极限.文中叙述了这一新方法的优点、基本原理和实验方法,并给出应用这方法测量一批光栅所得结果中的两个例子,结果表明,与通常所用直接扫描光谱线法所测结果相符合. 相似文献
7.
We optimize the room-temperature etching of InP using Cl2/CH4/H2 and Cl2/N2 inductively coupled plasma reactive ions. A design of experiment is used in the optimization. The results, in terms of etch rate, surface roughness and etched profile, are presented. These Cl2-based recipes do not require substrate heating and thus can be more cost effectively and widely applied. The Cl2/CH4/H2 process is able to give a higher etch rate (about 850 nm/min) and cleaner surface with less polymer formation compared to the conventional CH4/H2 process. The Cl2/N2 process produces even higher etch rate (as high as 2μm/rain), but rougher surface with slight sidewall undercut. The Cl2/N2 process also has no polymer formation due to the absence of methane gas. Both the processes give very good selectivity to the silicon dioxide (SiO2) etch mask. The selectivity of InP to the oxide mask (up to 55:1) for the Cl2/N2 process is one of the highest reported so far. The etched structures possess reasonably good sidewall verticality and surface quality comparable to that obtained under elevated temperature condition (〉 200℃). 相似文献
8.
1-羰基-1,2,3,4-四氢菲(Ⅰ)与二乙醇胺盐酸盐及36%甲醛水溶液在95%乙醇中进行Mannich反应,除得到Mannich碱1-羰基-2-[N-双(β-羟乙基)-氨次甲基]-1,2,3,4-四氢菲盐酸盐(Ⅱ)外,还得到少量的1-羰基-2-次甲基-1,2,3,4-四氢菲(Ⅲ)及其二聚物(Ⅴ)。此反应若在无水乙醇中进行,三小时内主要生成Mannich碱(Ⅱ)。反应时间若延长至廿小时以上,剐所得主要产物为二聚物(Ⅴ)。反应若在异戊醇中进行,虽仅一小时左右,亦生成较大量的副产物(Ⅴ)。化合物(Ⅱ)极不稳定,在甲醇-水溶液中稍热即失去胺基而成Ⅲ。Ⅲ在苯溶液中,以5%鈀-炭为催化剂,很顺利地氢化成1-羰基-2-甲基-1,2,3,4-四氢菲(Ⅳ)。Ⅲ的二聚物(Ⅴ)与羟氨盐酸盐不形成肟。Ⅰ与多聚甲醛在乙醇钠催化作用下缩合,形成2,2'-次甲基-双(1-羰基-1,2,3,4-四氢菲)(Ⅵ),此物经证明与Ⅴ有区别。Ⅰ与氮芥盐酸盐及36%甲醛水溶液在乙醇中反应生成1-羰基-2-[N-双(β-氯乙基)-氨次甲基]-1,2,3,4-四氢菲盐酸盐,由此可得相应的游离胺(Ⅶ)。 相似文献
9.
10.
Rates of solvolyses of 2-(4-methylphenyl)-2-propyl benzoate (2b), 2-(4-methylthiopheny1)-2-propyl benzoate (3b) and 2,2-dimethy1-1-(4-methoxypheny1)-1-phenyl-1-propy1 benzoate (4b) were measured, respectively, in ten or more different solvent systems. Additional YBnOPXB and Y, BnOPNB values in binary trifluoroethanol-water systems were determined, Grunwald-Winstein type correlation analysis showed that YBaIOBB values were applicable to benzylic benzoates. The rate ratio, koPNB/KOBZ, was found to be solvent-dependent in the range of 29 for 4 in ethanol to 4 for 2 in trifluoroethanol-water. Non-limiting mechanism, including both nucleophilic and electrophilic solvent assistance, in the solvolysis of 2b was discussed, 相似文献