在反转恢复测试中磁化矢量的演化特征:辐射阻尼效应  

INVERSION RECOVERY MEASUREMENTS: THE RADIATION DAMPING EFFECTS

作　　者：罗会俊[1] 王复[1] 诸培奋[1] 潘铁英[1] 史新梅[1] 

机构地区：[1]华东理工大学分析测试中心,上海200237

出　　处：《波谱学杂志》2000年第2期95-102,共8页Chinese Journal of Magnetic Resonance

摘　　要：在强辐射阻尼存在下 ,水样 ( 90 %H2 OinD2 O)的反转恢复实验表明 :当两脉冲的相位相差 1 80°且反转脉冲角 <1 80°时 ,或两脉冲相位一致但反转脉冲角 >1 80°时 ,在检测期观测到的信号强度将不发生从负极大值到正极大值的突变 ;在同样的条件下 ,如果存在频率偏置 ,信号强度存在波动 ,即beating效应 .只有当两脉冲的相位一致而反转脉冲角 <1 80°时 ,或两脉冲的相位相差 1 80°但反转脉冲角 >1 80°时 ,在检测期信号强度才发生突变 ,即jumping效应 .这些现象都可通过辐射阻尼理论予以合理地解释 .另外 ,在检测期当磁化矢量运动到 z轴附近 (对应于τ=Trdln{tan[(π±δ) /2 ]}) ,信号强度与理论预计的偏差实际上与T1In the presence of strong radiation damping, the conventional two pulse inversion recovery measurements have been performed on water sample(90%H\-2O/10%D\-2O). It shows that if two pulses in IR sequence are 180° out of phase and the flip angle of the inversion pule is smaller than 180°, or if two pulses are in phase and the flip angle of the inversion pulse is larger than 180°, the signal intensity will continuously changes with the recovery time. Conversely, if two pulses are in phase (or 180° out of phase) and the flip angle of the inversion pulse is smaller than 180° (or larger than 180°), the signal intensity will jump from the negative maximum to the positive maximum around \$τ=T\-\{rd\}\%ln{tan\%\[(π±δ)/2\]}.\$ Under the off resonance condition, no matter what pulse phase, the beating effect can be always observed, but the phase of the signal explicitly depends on the relative phase of the pulses. As a result, the phase cycling will greatly suppress the beating effect. These phenomena can be well explained by the radiation damping theory. In addition, when the magnetization locates near the -z axis during the detection, the deviation of theoretical expectation from the experimental data is closely related to the longitudinal relaxation effect.

关 键 词：反转恢复测试 T1弛豫 磁化矢量 辐射阻尼效应 

分 类 号：O482.53[理学—固体物理]