Dear Craig,
If you only have one signal (and either you can observe it directly or know
precisely where it is), then simple cw decoupling will suffice. If you do
not know exactly where it is but know approximately where it is, then Waltz
decoupling may suffice (ca. 10 kHz bandwidth depending on your selected
parameters) and can be applied for some seconds as it uses fairly low power.
Another low power decoupling sequence is adiabatic decoupling which has a
very large bandwidth but, depending on your system, it may not with run with
inverse-gated decoupling (zgig). On our Avance III it does not run so Bruker
sent me a sequence that will run (I have attached it since it not in the
standard Bruker-supplied library).
For calibration, you can either just take what the edprosol table gives you
(generally fine and for one off runs avoids the work of calibrating and should
be used in any case for adiabatic decoupling). My methodology for calibrating
pulse width and power is to 1. start with a typical pulse width, e.g. 60 us
for Waltz, 80-90 us for GARP, and measure over a suitable range of power levels
(chosen either from experience or use a value from edprosol as a guide).
2. The optimum power level can then be used to measure over a suitable range of
pulse widths. 3. Once the power level and pulse width have been optimized,
the bandwidth can be checked (or even for a selection of pulse widths). All
these measurements are done in an array fashion using popt in Bruker (or paropt
for older TopSpin/XWinNMR versions).
Comments on listed heteronuclei:
Pt195, due to its sizeable CSA, you will only see coupling at low field, e.g. << 9.4 T.
N14 you do not normally see coupling due to fast relaxation as it is a quadrupolar
nucleus; but coupling is present when the nucleus is in a symmetric environment,
in which case N14 is very easily observed directly.
Rh103 this is a difficult nucleus since its gamma is so low that unless you have
a special setup, sensitivity is exceedingly poor. Coupled with this, the chemical
shift range is huge and the chemical shift is very sensitive to the environment
so it shifts a great deal, thus even indirect observation can be problematic.
Finally, there does tend to be good (but not infallible) built-in protections for
applying too much power, nevertheless I would still try to keep the acquisition
time relatively short and use only inverse-gated decoupling with a decent amount
of delay time after the acquisition (pulse delay, relaxation delay, D1, PAD...
too many names).
Good luck,
Karel
________________________________________
> From: main_at_ammrl.groups.io on behalf of Craig Grimmer via groups.io
> Sent: 14 February 2026 12:29:50
> To: main_at_ammrl.groups.io
> Subject: [AMMRL] Advice on X-nucleus decoupling during 1-D 1H acquisition?
Good afternoon All
Does anyone have any advice on how to choose an appropriate probe-safe
heteronuclear (X) decoupling power level and decoupling scheme for use during
1-D proton experiments?
I don't mean X-decoupling during the short-duration AQ time in an n-D experiment;
I'm looking at multi-second X-decoupling during 1-D proton experiments, where X
is a low-band/low-gamma nucleus (e.g. 195Pt, 14N, 103Rh). Most of these X-nuclei
have a single resonance so excitation bandwidth is limited. I'm concerned about
potentially excessive decoupling power that may lead to sample heating and probe
damage. The normal spectrometer documentation doesn't seem to address this.
Thank-you,
Craig.
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Received on Sat Feb 14 2026 - 15:29:36 MST