射频场照射下多自旋体系弛豫的理论计算

Theoretical description and numerical computationof the relaxation of multi-spin system in the presence of an RF field

根据Liouville-von Neumann方程,对射频场照射下多自旋体系的弛豫进行了理论描述,并用WBR理论推导出了体系的弛豫方程组,给出了各类弛豫速率的理论计算公式.在此基础上,编制了弛豫方程组数值解的计算程序,分别用此程序和Bloch方程计算了双自旋体系在不同情况下的稳态解,并对计算结果进行了简要的分析和讨论.

According to the Liouville-von Neumann equation and WBR theory, a general description of relaxation of multi-spin system in the presence of an RF field is given. The relaxation equations are deduced and the theoretical computational formulas of various relaxation rates are obtained. It is almost impossible to access the analytical solutions of relaxation equations, so the computer program for numerical solutions is developed. By means of the program and the Bloch equations, the steady state solutions of two-spin system under various conditions are computed and these solutions are briefly discussed.