摘要
采用一高温超导射频量子干涉器(HTS rf-SQUID)作为信号探测器件,研究了多种液体样品的低场核磁共振信号。通过改变测量场(简称Bm)的大小,可以探测到质子拉莫频率(简称fL)从2Hz到40kHz的信号。由于在低场核磁共振中,Bm的均匀性能很好的得到满足,因而可能得到很窄的谱线宽度。实验发现,对自来水样品,在7μT以下均可接近谱线的自然宽度。同时,在低场核磁共振条件下,样品的化学位移很小以至于消失,因而可以研究"纯"的异核间的自旋耦合谱。作者研究了低场下2,2,2-三氟乙醇的低场自旋耦合谱。另外,作者首次采用SQUID在户外探测到地球磁场下的核磁共振现象,并研究了地球磁场的涨落对测量的影响,为SQUID的低场核磁共振研究开辟了一个新的研究方向。
High -resolution low -field nuclear magnetic resonance （NMR） signals of selected liquid samples were recorded using a nitrogen -cooled superconducting quantum interference device （SQUID）. The NMR measurements were performed at Larmor frequencies （fL） from 2Hz to 40kHz. The natural spectrum line width of tap water could be measured in magnetic fields below 7 microtesla. The ＂ pure＂ J- coupling spectrum of 2,2,2 -trifluoroethanol was recorded at different measurement fields, with signals separated by several hundred Hz, to demonstrate the measurement sensitivity and resolution. Using the same SQUID magnetometer, some low field NMR measurements were performed under the Earth＇s magnetic field, and the influence of field fluctuation was investigated.
出处
《低温与超导》
CAS
CSCD
北大核心
2008年第11期29-33,共5页
Cryogenics and Superconductivity
