Contributions to the Gaussian line broadening of the proxyl spin probe EPR spectrum due to magnetic-field modulation and unresolved proton hyperfine structure
Contributions to the Gaussian line broadening of the proxyl spin probe EPR spectrum due to magnetic-field modulation and unresolved proton hyperfine structure
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DOI：
10.1006/jmre.1998.1414
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发表时间：
1998-06-01
影响因子：
2.2
通讯作者：
Lamy-Freund, MT
中科院分区：
文献类型：
--
作者：
Bales, BL;Peric, M;Lamy-Freund, MT
导出一个简单的表达式来计算通过正弦磁场调制加宽的Voigt线的总高斯线宽，如下所示：Δ H-pp（G）（H-m）（2）= Δ H-pp（G）（0）（2）+ kappa（2）H（m）（2），其中Δ H-pp（G）（H-m）是用调制幅度H-m/2观察到的高斯线宽，并且Δ H-pp（G）（0）是高斯线。在零调制的极限宽度。场调制贡献了kappa H-m的附加高斯加宽，其中kappa是常数，其与Δ H-pp（0）（0）正交相加以给出总高斯线宽。表示在没有Δ H-pp（0）（0）的调制加宽的情况下Voigt线的总线宽，通过分析手段和光谱模拟两者示出，常数kappa在H-m远小于Delta H-pp（0）（0）的极限下等于1/2;然而，使用与Delta H-pp（0）（0）一样大的H-m值只会导致与kappa = 1/2的微小偏差。该制剂对洛伦兹线和Voigt线均有效，并在CCl 4和水性缓冲液中对2，2，5，5-四甲基吡咯烷-1-氧基-3-羧酸（3-羧基乙基）进行了测试。这种自旋探针进行了研究，因为乙酰基基团是唯一的主要自旋探针部分，其高斯线宽尚未在文献中进行了表征。对于3-羧基乙酰基，发现Δ H-pp（G）（0）= 1.04 +/- 0.01 G，与溶剂极性无关。在9.5 ℃下，3-羧基肉豆蔻基的N-14超精细偶联常数的精密度值如下：在CCl 4中为14.128 +/- 0.001 G，在水性缓冲液中为16.230 +/- 0.002 G。Delta H-pp（G）（0）和N-14超精细耦合常数的温度依赖性被报告为经验方程。本工作的结果与以前公布的数据一起允许准确校正的影响，不均匀的加宽由于未解决的超精细结构和调制加宽的大多数自旋探针在常用的。(C)北京：科学出版社.
A simple expression is derived to compute the total Gaussian linewidth of a Voigt line that is broadened by sinusoidal magnetic-field modulation as follows: Delta H-pp(G)(H-m)(2) = Delta H-pp(G)(0)(2) + kappa(2)H(m)(2), where Delta H-pp(G)(H-m) is the Gaussian linewidth observed with an modulation amplitude H-m/2 and Delta H-pp(G)(0) is the Gaussian line-width in the limit of zero modulation. The field modulation contributes an additional Gaussian broadening of kappa H-m, where kappa is a constant, which adds in quadrature to Delta H-pp(G)(0) to give the total Gaussian linewidth, Denoting the overall linewidth of the Voigt line in the absence of modulation broadening by Delta H-pp(0)(0), it is shown, both by analytical means and by spectral simulation, that the constant kappa is equal to 1/2 in the limit of H-m much less than Delta H-pp(0)(0); however, using values of H-m as large as Delta H-pp(0)(0) leads to only minor departures from kappa = 1/2. The formulation is valid both for Lorentzian and Voigt lines and is tested for 2,2,5,5-tetramethylpyrrolidin-1-oxyl-3-carboxylic acid (3-carboxy proxyl) in CCl4 and in aqueous buffer. This spin probe was studied because the proxyl group is the only major spin-probe moiety whose Gaussian linewidth had not been characterized in the literature. For 3-carboxy proxyl, it is found that Delta H-pp(G)(0) = 1.04 +/- 0.01 G independent of solvent polarity. Precision values of the N-14 hyperfine coupling constant for 3-carboxy proxyl at 9.5 degrees C are as follows: 14.128 +/- 0.001 G in CCl4 and 16.230 +/- 0.002 G in aqueous buffer. The temperature dependence of Delta H-pp(G)(0) and the N-14 hyperfine coupling constant are reported as empirical equations. Results of the present work taken together with previously published data permits accurate correction for the effects of inhomogeneous broadening due to unresolved hyperfine structure and modulation broadening for the majority of spin probes in common use. (C) 1998 Academic Press.