HI Weixing,
this looks like radiation damping returns water back to +Z towards the end
of the experiment when d0 gets really long. Flipping the sequence to have
the gradient first dephases the water magnetization.
You should also be able to put a gradient between the 90 1H and 90 13C pulses.
At that point magnetization of interest should be IzSz and water is Iy a
gradient at this time will dephase it.
These high-Q probes give you great sensitivity but radiation damping is
something you have to take into account.
Clemens
On 3/11/2026 1:30 PM, Zhang, Weixing via groups.io wrote:
Dear All,
I am running an HSQC experiment of glucose in 90% H₂O / 10% D₂O
using a long d₁ delay.
During acquisition, the FID became dominated by noise toward the end. After
I inverted gp1 and placed it immediately after the first ¹³C 90° pulse,
this issue disappeared and the water suppression improved noticeably.
However, AI-based software tools do not recommend this modification.
I have not observed any differences in the resulting spectra, but I would
appreciate any comments or insights you may have on this adjustment.
Best regards,
Weixing
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Received on Wed Mar 11 2026 - 11:38:03 MST