Classification of relaxation time
There are two types of relaxation time, t1 and t2
t1 is the spin lattice or longitudinal relaxation time, the time constant T1 of the longitudinal magnetization recovery is called the longitudinal relaxation time (also known as spin-lattice relaxation time)
t2 is spin-spin or lateral relaxation time, and the time constant T2 of the disappearance of transverse magnetization is called lateral relaxation time (also called spin-spin relaxation time).