I received following email from Clemens Anklin, pointing out a neat trick to
overcome Ernst Angle problem with the spin echo detection. Thank you,
Clemens.
Hsin
-----Original Message-----
From: Clemens Anklin [mailto:clemens.anklin_at_bruker-biospin.com]
Sent: Wednesday, August 20, 2008 10:37 PM
To: hsin.wang_at_sci.ccny.cuny.edu
Subject: Re: AMMRL: C13 detect on a C13-cold cold probe on INOVA: Summary
Dear Hsin
you can overcome the issue with the Ernst angle by setting the pulse to
the "Ernst angle" + 90 degrees. The 180 degree pulse then takes this to
-"Ernst angle" and the magnetization can recover from about the same
angle just from the other side.
Regards
Clemens
>
>
> 1) Several people pointed out that methods relying on linear prediction
> are not perfect (there is often a small dip in the baseline around
> 20-40ppm) and the best way to avoid the long delay is to use spin-echo.
> There are several sequences in Biopack to accomplish this. The problem
> is that if one wants to use Ernst Angle the 180 pulse inverts a large +Z
> component to -Z and effectively increases the delay needed for the
> relaxation recovery. This makes Ernst Angle optimization unusable. A
> better way is to invert the C13 spin in the beginning of the sequence as
> demonstrated in the "z-restored spin echo" paper by Xia et al, MRC 2008;
> 46: 432-435. I attempted to code the sequence, but have not made it to
> work. The paper described in detail the use of chirp pulses for Bruker
> instruments but not very clear (to me) for wurst pulses on Varian. It
> is likely I did not use them properly. I probably should have use the
> simple composite pulse instead.
>
>
--
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Clemens Anklin Ph.D. Vice President
Bruker BioSpin NMR Applications & Training
15 Fortune Drive Phone: 978 667 9580 ext 5144
Billerica MA 01821 Fax: 978 667 2955 skype_ID: canklin
web: www.bruker-biospin.com e-mail: clemens.anklin_at_bruker-biospin.com
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Received on Thu Aug 21 2008 - 03:59:34 MST