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I am running a varian gemini 300 on SUN microsystems with UNIX. I am trying to lock on my sample, and my lock is not showing up as a "step" as usual. Instead, it has troughs in it. What are some options in fixing this, or is this acceptable?

-Jon K.

asked Jun 06 '11 at 14:54

MONOJON's gravatar image


This sounds as if there is more than one deuterium resonance in the solvent. Which solvent does it happen with? - Jerry Hirschinger (Jun 09 '11 at 09:17)

I tried running a sample of pure D20 and still had this problem. Is the age of the D20 is an issue? Could moisture contamination result in this as well? - MONOJON (Jun 13 '11 at 07:52)

No. What is the Lock Power? Too much lock power will cause the lock level to oscillate. If not that, then I would suspect a bad power supply. - Jerry Hirschinger (Jun 16 '11 at 09:46)

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That means lock is not tuned, nothing unusual, the lock frequency depends on the sample and the tube.

Take a look at this document, it attempts to walk you through the locking procedure with vnmr.


answered Jun 07 '11 at 10:43

Evgeny%20Fadeev's gravatar image

Evgeny Fadeev

updated Jun 07 '11 at 10:43

I have been attempting to adjust the lock using this technique. I am still unable to remove the troughs from the lock signal. How do I "tune" the lock; are you refrencing a technique outside of standard sample locking? - MONOJON (Jun 13 '11 at 07:53)

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Is there a provision for displaying the lock channel (CW-)NMR signal by a field sweep modulation? It is then possible that a small amplitude of modulation of NMR signal is still occurring, even after lock is turned "ON". Reduce the "amplitude of modulation" to zero manually or switch off the modulation manually after turning lock "ON" when the "Peaks & troughs" any present might disappear.



answered Jun 11 '11 at 03:48

SankarampadiAravamudhan's gravatar image


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Asked: Jun 06 '11 at 14:54

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Last updated: Jun 16 '11 at 09:46

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