Hi,
I try to start an introduction to relaxation for less NMR experienced people.
The funny thing is: I believed to understand the basics of relaxation.
Now preparing an explanation as easy as possible for other people I have to
acknowledge, that simple things are by no means simple to understand.
At least seen from my point of view. I had a look into many textbooks,
but found no satisfying answer for two questions.
The basics of relaxation are fluctuating magnetic fields caused by
mechanical motions of the molecule while fixing the spins by the
strong external B0 field. A lot of pictures are available to illustrate
this effect. But ... we need electromagnetism. What is the source for
the oscillating electrical field?
T2. The vectorial presentation of dephasing is easily explained.
You are able to understand this assuming local variations of B0.
That's o.K. for T2 contribution coming from the instrument.
You cannot take the local oscillations from the molecule, because any
frequency of these oscillations would be a reason for T2 using
this model.
On the other hand you can use energy level diagrams and flip
flop processes and you understand the reason to need very
low frequent (electro)magnetic oscillations with a fixed frequency.
But is there a possible link between both models?
Maybe it is simply impossible to create pictures especially for the
T2 issue. But maybe you know an easy answer ...
Greetings
Rainer
Received on Sun May 08 2011 - 20:11:20 MST