3 SETTING OF INSTRUMENT CONDITIONS
CAUTION
•
Carefully read the instruction manual then perform the magic angle
spinning.
There is a danger of destroying the probe.
Heating the sample tube and its temperature calibration when in high-speed
When the sample rotates at a high speed, the rate of temperature increase is approxi-
mately the square of the spinning speed. The temperature increase depends on the indi-
vidual sample tube.
Moreover, depending on the temperature increase, a temperature gra-
dient appears; therefore, you need to be aware of this factor.
If you need to estimate the temperature gradient precisely, perform the temperature cali-
bration. The calibration should be on the individual sample tube with the bearing gas
pressure that you routinely apply.
Refer to the following literature for the temperature calibration.
A. Bielecki and D. P. Burum,
J. Magn. Reson. A 116, 215
–
220
(1995).
T. Takahashi, H. Kawashima, H. Sugisawa and T. Baba, Sold State Nuc. Magn.
Reson., 15
(2), 119
(1999).
For the calibration of the temperature, use
a lead nitrate sample.
The amount of shift in lead nitrate is 0.753 ppm/
℃
.
The following figure shows an example of a temperature calibration curve.
•
Sample tube:
Silicon nitride
•
Gas: Dry
air
•
Pressure of bearing gas: 0.15 MPa
•
Gas temperature:
Room temperature (25
℃
)
The vertical axis is the rate of a temperature increase based on the temperature when the
sample tube is at the minimum speed (in this case 5 kHz).
y = 0.1766x
2
- 0.8987x +
0.5105
R
2
= 0.9991
0
5
10
15
20
25
30
35
0
10
20
Spinnig rate（ｋＨｚ）
△T
em
p(
℃）
When you perform a variable temperature measurement, take the temperature in-
creases due to spinning into consideration, and set up the temperature so that the
temperature of the sample tube does not exceed the specification for the probe. If the
spinning speed approaches top speed, the temperature of the sample will be consid-
erably higher than the temperature shown on the display.
3-2
NMECAXS_V50-SLD-2
