| 查看: 3741 | 回复: 8 | |||
| 当前只显示满足指定条件的回帖，点击这里查看本话题的所有回帖 | |||
tianwei1332铁杆木虫 (著名写手)
|
[交流]
【讨论】MAS NMR什麽含义 已有7人参与
|
||
| MAS NMR什麽含义？是不是固态核磁共振？能给出什麽信息？ |
回复此楼» 猜你喜欢
企业为什么一定要做“专精特新”认定？如何成为专精特新企业？
已经有5人回复
-
求助ASIQwin新版本的软件
已经有0人回复
-
化学工程及工业化学论文润色/翻译怎么收费?
已经有291人回复
-
求全国高速分析学术交流会论文集
已经有2人回复
-
期待科研合作，共同发表论文
已经有215人回复
-
如何掌握一门外语？
已经有25人回复
-
国家级人才团体课题组招收2026届博士
已经有1人回复
-
气相色谱点不着火
已经有1人回复
-
化工安全有关的复习提纲
已经有0人回复
-
国家级人才课题组招收2026年入学博士
已经有2人回复
» 本主题相关价值贴推荐，对您同样有帮助:
- 那位高人指点下这三条线有什么区别，代表怎样的含义
已经有9人回复
- 咨询一下公益基金应急性、基础性、培育性的具体含义
已经有6人回复
- 关于灭菌参数Z值含义的疑问？
已经有4人回复
- A260/A280和A260/A230的含义
已经有19人回复
- 请问这张地球化学图里面的区域分别代表什么含义？
已经有3人回复
- 求助解析晶体结构的一些数据含义
已经有2人回复
- 【求助】高分子中MAS-NMR是指固态核磁吧？
已经有7人回复
- 博士的含义是什么？
已经有22人回复
- 【交流】DMA损耗角正切峰值高度的物理含义
已经有19人回复
- NCBI blast 结果一些参数的含义求高手指点
已经有12人回复
aust_jhe
至尊木虫 (著名写手)
- C-EPI: 1
- 应助: 62 (初中生)
- 金币: 17354.5
- 红花: 9
- 帖子: 1192
- 在线: 209.6小时
- 虫号: 430372
- 注册: 2007-08-05
- 性别: GG
- 专业: 催化化学
★ ★ ★ ★
小木虫(金币+0.5):给个红包，谢谢回帖交流
liconglin970410(金币+3):多谢，欢迎常来交流 2010-06-08 14:27:17
小木虫(金币+0.5):给个红包，谢谢回帖交流
liconglin970410(金币+3):多谢，欢迎常来交流 2010-06-08 14:27:17
|
MAS NMR Magic Angle Spinning Nuclear Magnetic Resonance In nuclear magnetic resonance, magic angle spinning (MAS) is a technique often used to perform experiments in solid-state NMR spectroscopy. By spinning the sample (usually at a frequency of 1 to 70 kHz) at the magic angle θm (ca. 54.74°, where cos2θm=1/3) with respect to the direction of the magnetic field, the normally broad lines become narrower, increasing the resolution for better identification and analysis of the spectrum. In any condensed phase, a nuclear spin experiences a great number of interactions. The main three interactions (dipolar, chemical shift anisotropy, quadrupolar) often lead to very broad and featureless lines. However, these three interactions in solids are time-dependent and can be averaged by MAS. The nuclear dipole-dipole interaction, between magnetic moments of nuclei averages to zero only at the magic angle, θm . The chemical shift anisotropy, a nuclear-electron interaction, averages to a non-zero value. The quadrupolar interaction is only partially averaged by MAS leaving a residual secondary quadrupolar interaction. In liquids, e.g. a solution of an organic compound, most of these interactions will average out because of the rapid time-averaged molecular motion that occurs. This orientation averaging in solution is mimicked by MAS of a solid. This causes the signal to become much narrower, giving rise to the isotropic value (which is of interest for structural determination of solid materials and compounds) and spinning sidebands which occur at multiples of the spinning speed and can be used to determine the chemical shift anisotropy of the nuclei. The physical spinning of the sample is achieved via an air turbine mechanism. These turbines (or rotors) come in a variety of diameters (outside diameter), from 2.0-15.0 mm, and are usually spun on air or nitrogen gas. The rotors are made from a number of different materials such as ceramics e.g. zirconia, silicon nitride or polymers such as poly-methyl-methacrylate (PMMA), polyoxymethylene (POM). The cylindrical rotors are axially symmetric about the axis of rotation. Samples are packed into the rotors and these are then sealed with a single or double end cap. These caps are made from number of different materials e.g. Kel-F, Vespel, zirconia or boron nitride depending on the application required. |
4楼2010-06-02 18:51:43