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Recently while getting a loaner probe up and running, I noticed that the engineers simply had me set the decouple 90 to the same as the regular 90. I was under the impression that you wanted to use a lower power pulse for decoupling. Is setting the decoupling 90 to the same bascially a 'good enough' shortcut? If so, what's a better way to do it? and to determine it? |
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I'm wondering if you are conflating two separate calibrations. People loosely use the term "decoupler pulse" to refer to either a lower power pulse used as the basis for broadband decoupling sequences (like WALTZ or GARP), or to refer to a high-power pulse used on the second channel of a sequence (e.g. 1H on a C-H HETCOR). In the latter case, with a newer instrument, there is essentially no difference between an observe or "decouple" 90. In the former case, you are certainly correct that you want pulses of much lower power (< 5 W for 1H on a standard liquids probe, in most cases much less). The best calibration procedure depends on the type of instrument. For a general, approximate check, you can choose a reasonable power level (say 1 W nominal for 1H on the outer coil of a 5 mm liquids probe), and obtain a value for an observe 90 degree pulse at that low power. That may well be close enough to the correct setting to give you tolerable decoupling for a WALTZ sequence, for instance. |
