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首頁> 外文學(xué)位 >Multiple quantum magic-angle spinning NMR with cross-polarization: Spectral editing of high-resolution spectra of half-integer quadrupolar nuclei.
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Multiple quantum magic-angle spinning NMR with cross-polarization: Spectral editing of high-resolution spectra of half-integer quadrupolar nuclei.

機譯：具有交叉極化的多量子幻角旋轉(zhuǎn)NMR：半整數(shù)四極核的高分辨率光譜的光譜編輯。

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摘要

n experiment is presented that combines the techniques of multiple-quantum magic-angle spinning (MQMAS) and cross-polarization (CP) between spin-1/2 and half-integer quadrupolar spin nuclei. This technique, referred to as CP MQMAS, allows the coordination of the spin-1/2 nuclei within a quadrupole system to be determined, which demonstrates its usefulness for spectral editing. The radio-frequency (rf) pulse sequences and necessary phase-cycling are developed and examined. A novel approach of incorporating a 'z-filter' between the two techniques allowed us to optimize our new procedure, CP MQMAS, as two unique experiments prior to their coupling. Experimental details concerning the manipulations necessary to produce and detect multiple-quantum (MQ) NMR spectra of half-integer quadrupole nuclei are presented. Additionally, the spin dynamics of CP from a spin-1/2 nucleus to the central transition of a quadrupolar nucleus during magic-angle spinning (MAS) are examined. For quadrupolar systems the CP process operates most efficiently using very low rf field strengths, which is markedly different than that used in conventional CP between spin-1/2 nuclei. When low rf field strengths are used, no longer can the Hamiltonians from the second-order quadrupolar interaction, MAS speed and carrier frequency(s) offset be treated as negligible. Finally, as the MQMAS technique requires very high rf field strengths, and CP very low rf field strengths, it can be seen that the CP MQMAS technique demands high-quality linear power amplifiers.;As a preliminary test of the CP MQMAS experiment, we chose ;Our second CP MQMAS experiment was accomplished using
機譯：提出了一項結(jié)合多量子幻角旋轉(zhuǎn)（MQMAS）和自旋1/2和半整數(shù)四極自旋核之間的交叉極化（CP）技術(shù)的實驗。這項技術(shù)被稱為CP MQMAS，可以確定四極桿系統(tǒng)中自旋1/2原子核的配位，這證明了其在光譜編輯中的有用性。開發(fā)并檢查了射頻（rf）脈沖序列和必要的相位循環(huán)。在這兩種技術(shù)之間結(jié)合使用“ z濾波器”的新穎方法使我們能夠優(yōu)化新程序CP MQMAS，因為這是兩個獨特的實驗，它們需要進行耦合。提供了有關(guān)產(chǎn)生和檢測半整數(shù)四極核的多量子（MQ）NMR光譜所需的操作的實驗細節(jié)。另外，還研究了在幻角旋轉(zhuǎn)（MAS）期間CP從自旋1/2原子核到四極核中心過渡的自旋動力學(xué)。對于四極系統(tǒng)，CP過程使用非常低的rf場強才能最有效地運行，這與自旋1/2原子核之間的常規(guī)CP所使用的場強明顯不同。當(dāng)使用低rf場強時，不再可以忽略來自二階四極相互作用，MAS速度和載波頻率偏移的哈密頓量。最后，由于MQMAS技術(shù)要求很高的RF場強，而CP要求非常低的RF場強，因此可以看出CP MQMAS技術(shù)需要高質(zhì)量的線性功率放大器。;作為CP MQMAS實驗的初步測試，我們選擇；我們的第二個CP MQMAS實驗使用

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  • 作者

    Lang, David Patrick.;

  • 作者單位

    Iowa State University.;

  • 授予單位 Iowa State University.;
  • 學(xué)科 Chemistry Physical.
  • 學(xué)位 Ph.D.
  • 年度 1998
  • 頁碼 121 p.
  • 總頁數(shù) 121
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類
  • 關(guān)鍵詞

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