Proton spin T1 relaxation dispersion in liquid H2O by slow proton‐exchange
Proton spin T1 relaxation dispersion in liquid H2O by slow proton‐exchange
复制标题
通过缓慢质子交换在液态水中质子自旋 T1 弛豫分散
DOI：
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发表时间：
1980
期刊：
影响因子：
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通讯作者：
G. Béné
中科院分区：
文献类型：
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作者：
V. Graf;F. Noack;G. Béné
我们通过场循环技术测量了纯水中纵向质子自旋弛豫时间T1作为温度（10、37、80°C）和拉莫尔频率（50 Hz ~ 0 ~ 50 kHz）的函数。由于不同氧环境（16 O、17 O、18 O）之间的缓慢质子交换，T1在低于ν0 ~ 5 kHz时变得依赖于频率，这调制了磁性1H-17 O相互作用。质子交换时间τe被发现是Arrhenius型的，活化能为13.4 kJ/mol，指前为1.5×10−6 s（37 °C：τe=2.6×10−4 s）。这是在相当好的协议与以前在文献中获得的结果，通过更间接的NMR方法。新的质子交换降低了实验误差限制，并允许在非常小的频率下进行测量，熟悉的T1ρ技术不再起作用。
We have measured the longitudinal proton spin relaxation time T1 in pure water as a function of temperature (10, 37, 80°C) and Larmor frequency (50 Hz⩽ν0⩽50 kHz) by means of field‐cycling techniques. T1 becomes frequency dependent below ν0≈5 kHz due to the slow proton‐exchange between different oxygen environments (16O, 17O, 18O), which modulates the magnetic 1H–17O interaction. The proton‐exchange time τe was found to be Arrhenius‐like with activation energy 13.4 kJ/mol and pre‐exponential 1.5×10−6 s (37 °C:τe=2.6×10−4 s). This is in fairly good agreement with results obtained previously in the literature by more indirect NMR methods. The new access to proton‐exchange reduces the experiemtnal error limits and allows measurements at extremely small frequencies, where the familiar T1ρ technique no longer works.