Date: Wed, 25 Mar 2020 14:38:02 +0100
Dear all,
Hope everybody is doing well in these very bad times and that things will
get better soon.
In the meantime, I hope you can help with the following.
Recently we have faced a new (baseline) problem in recording 1D Sn NMR
spectra, working on a H-X MAS probe.
On the same probe, previously, we have recorded analogous spectra (i.e.
zg30, hpdec with 1H decoupling) with quite satisfying results.
However, after one technical intervention, where the preamp configuration
was changed (we switched from a 1000W to a 500W preamp on X, and we also
changed routing, ie we exchanged X-channel from TRX3 to TRX2), we are
encountaring some troubles. In particular, the baseline looks like very
distorted. Also, we are reporting a lower power efficiency, as the 90
degree pulse seems to be increased from 3.8us to 9us (at the same power,
150W).
The acquisition parameters are exactly the same as before, large spectral
width, long dead time and short dwell time. I have attached you two
screenshots showing spectra before and after. Of course this is the best
scenario, using a "standard" sample (SnI2) with a good si/no ratio. Moving
to different samples, things get worse and signals are hidden in this sort
of ringing pattern.
Thanks in advance.
Best wishes
Alessia
(image/png attachment: original_spectrum.png)
(image/png attachment: distorted_baseline.png)