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9 ~(13)C自旋-晶格弛豫时间(T_1)的测量及应用 9.1 测定T_1的方法 9.1.1 倒向—恢复法此法是用(180°-τ-90°)_n脉冲系列作用于样品。磁化矢量M_0在180°脉冲作用下倒向(图20b),在自旋-晶格弛豫过程中,磁化矢量从-M_0经0到+M_0弛豫,在这一过程中,即过了时间τ后,90°脉冲将部份弛豫的磁化矢量M_τ旋转到X(?)Y平面中,并在接收线圈中感应出FID信号。如果τ很短,M_τ还是负的(M_τ<0),90°脉冲(?)_1,作用后M_τ沿X向负Y轴旋转(图20c),
9 ~ (13) C Measurement and Application of Spin-Lattice Relaxation Time (T_1) 9.1 Methods for Determining T_1 9.1.1 Reverse-Recovery Method This method uses the (180 ° -τ-90 °) _n pulse series Acting on the sample. The magnetization vector M_0 is reversed by a 180 ° pulse (Figure 20b). During the spin-lattice relaxation, the magnetization vector relaxes from -M_0 through 0 to + M_0, during which time After τ, the 90 ° pulse rotates the partially relaxed magnetization vector M_τ into the X (Y) Y plane and induces a FID signal in the receiver coil. If τ is short, M_τ is still negative (M_τ <0), 90 ° pulse (?) _ 1, and M_τ rotates along negative X axis (Fig. 20c)