Hi,
the radiation damping does not depend on the flip angle. The general NMR assumption
that the resonance circuit is independent of the sample magnetization does not hold
for high Q and strong magnetization. So the frequency difference reporting the
temperature will be wrong for any detection.
Best regards,
- Bernd -
On Tue, Aug 22, 2023 at 14:31, Donghui Wu via groups.io wrote:
Hello Weixing,
If radiation damping is the problem, you might be able to get a spectrum without
its effect by using the shortest pulse width with lowest level of RF power possible,
i.e. a very very small flip angle. This will let you use the calibration sample you
already have (80% ethylene glycol) and the well established NMR temperature measurement
parameters.
Regards,
Donghui
On Tue, Aug 22, 2023 at 1:03=E2=80=AFPM Zhang, Weixing via groups.io wrote:
Dear All,
Thanks to everyone who has read and replied to my email.
We want to use a CryoProbe to run experiments at different temperatures up to 90 oC (363 K).
Many people think that radiation damping of 80% ethylene glycol is the problem.
Massively detuning the cryoprobe or using deuterated ethylene glycol should give more accurate results.
Clemens told me that the Bruker part number of 99% ethylene glycol-d6 is Z10629.
Z10629 is currently under development in Germany and it would be about a month for it to be completed.=20
The Bruker AU program calctemp has these options.
I am curious where Bruker got the equations from, and I would greatly appreciate any information.
With warm regards,
Weixing Zhang (Walter)
Research Operation Manager
Biomolecular NMR Spectroscopy Center
St. Jude Children=E2=80=99s Research Hospital
Memphis, TN 38105
USA
> From: main_at_ammrl.groups.io (mailto:main_at_ammrl.groups.io) On Behalf Of Clemens Anklin via groups.io
> Sent: Friday, August 18, 2023 2:26 PM
> To: main_at_ammrl.groups.io (mailto:main_at_ammrl.groups.io)
> Subject: Re: [AMMRL] 99.8% MeOD vs 80% Ethylene Glycol
Hi Weixing
if you do this on a cryoprobe this will be the expected result. 80% Glycol
gives a massive amount of radiation damping. This leads to different readings
as shown by Stefan Berger in
https://doi.org/10.1002/mrc.1941
You can try to run a more accurate measurement by massively detuning the probe.
With best regards
Clemens
On 8/18/2023 3:09 PM, Walter Zhang wrote:
Dear All,
I need to use 80% Ethylene Glycol for high temperature calibration.
Before I do the calibration, I compared it with 99.8% MeOD at 303 K.
When I set temperature to 303 K,=20
99.8% MeOD gives 303.03 K while 80% Ethylene Glycol gives 300.57 K
The difference between the two calibration samples is 2.46 K.
Is this normal?
Your comments are appreciated!
Best regards,
Weixing Zhang
St. Jude Children=E2=80=99s Research Hospital
Memphis, TN 38105
USA
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Received on Tue Aug 22 2023 - 15:01:32 MST