6 MEASUREMENT OF RELAXATION TIME
6.3 RELAXATION TIME MEASUREMENT OF
13
C BY
TORCHIA METHOD
One technique for measuring the relaxation time of a solid sample is the Torchia method.
The relaxation time is obtained by measuring the differences
between the spectra by the
inversion-recovery method using CP and the spectrum by the CPMAS method. Since the
CPMAS method is used, the waiting time can be shortened compared with the relaxa-
tion-time measurement by direct observation.
For a peak that changes by a single exponential function, the strength of the magnetiza-
tion M (
τ
) is expressed as a function of the relaxation delay time (
τ
) by the following for-
mula.
M (
τ
) = M
0
exp(-
τ
/T
1
)
1.
Load the pulse sequence
torchiaT1_cpmas.jxp
into
Experiment Tool
.
2.
Set scans to a multiple number of two.
3.
Set the array parameters for
interval
based on the estimated T
1
value.
Setup the array variable for performing the Torchia method in decreasing order. The
arrow buttons enable you to switch between increasing and decreasing order.
4.
Click the
Set Value
button.
The array parameter window closes, and the values you set are entered into
interval
in the
Experiment Tool
.
5.
Click the
Submit
button.
The measurement starts.
Although data-processing procedure is the same as that for the inversion-recovery method,
use the following approximation formulas.
Weighted Linear Spin Lock:
The weighted linear least squares method
The weight is reduced for the measurements hav-
ing long
τ
.
Unweighted Linear Spin Lock:
Linear least-squares method without weights
Nonlinear Spin Lock:
Nonlinear least-squares method
Refer to the user’s-manual “Application” for information about the measurement and
processing of the inversion-recovery method.
6-4
NMECAXS_V50-SLD-2
