JNM-ECA Series JNM-ECX Series JNM-ECS Series - George Fox ...

1 RELAXATION TIME MEASUREMENT
1.1 RELAXATION TIME MEASUREMENT
There are three kinds of relaxation times, T 1 , T 1ρ , and T 2.
Section 1.1 explains the method of T 1 measurement, which is frequently performed.
1.1.1 Relaxation Time (T 1 ) Evaluation
To obtain T 1 with high accuracy, array measurement is performed using the variable of
recovery times. To set the variable of recovery times to appropriate values, the
approximate T 1 of the sample must be determined first.
This section describes the method of a simple T 1 evaluation by means of inversion
recovery.
■ Simple T 1 evaluation method using T 1 measurement mode by means of
inversion recovery
If a peak changes as a single exponential function, the observed magnetization M(τ) is
expressed as a function of the relaxation delay time τ by using the inversion recovery
method:
M (τ) = M 0 {1-2exp(-τ/ T 1 )}
From this equation it is found that T 1 can be evaluated from the delay time when the
observed magnetization becomes zero. This delay time is called the null point, and is
represented by τ null .
Thus, T 1 is given by
T 1 = τ null / ln2 = 1.44 × τ null
To obtain an accurate value of T 1 , first obtain the null point, and then perform the array
measurement .
NMECA/ECX-USA-3 1-1