i like this post (click again to cancel)
0
i dont like this post (click again to cancel) remove favorite mark from this question (click again to restore mark)

how T1 and T2 relaxation time depend on nmr signal?

asked Oct 21 '13 at 00:59

shine%20a's gravatar image

shine a
1


2 Answers:
i like this answer (click again to cancel)
1
i dont like this answer (click again to cancel)

Well, if nobody else answers... T2 is related to NMR spectrum width in solids and viscous liquids, spectrum half-width is approx. equal to 2/T2. I believe T1 is unrelated to the spectral shape. But the spectra one gets are depending on T1 and T2 severily. If relaxation delay in experiment is short (usually comparing to 5*T1), the signal will be weak. If one shortens T2 (say, dissolving a paramagnetic component in a liquid sample), the lines will be broaden.

link

answered Oct 23 '13 at 02:03

asbest's gravatar image

asbest
11

i like this answer (click again to cancel)
0
i dont like this answer (click again to cancel)

The question sounds backwards. Take a look at the classic "Pulse and Fourier Transform NMR" by Ferrer and Becker

T1 and T2 are time constants that come from the phenomenological bloch equations. T1 determines how much signal we detect. Waiting 5*T1 allows the spins to return to thermal equilibrium before the next perturbation. T2 is the time constant for decay in the transverse plane. In practice, T1 effects the signal more than T2. T2 can be used to find M(t=0) if you want to quantify signal amplitude.

Relaxation enhancement agents such as paramagnetic species can effect T1 and T2 differently and are more commonly used to decrease T1 so we do not have to wait. e.g., H2O has T1=T2=2.5s on my instrument (100MHz). When I dope with 1ppm CuSO4 * 5H2O I measure T1=0.28 T2=0.25 now 5*T1 is a reasonable 1s wait time :)

link

answered Oct 29 '13 at 07:39

w101bdk's gravatar image

w101bdk
7

Your answer
Please start posting your answer anonymously - your answer will be saved within the current session and published after you log in or create a new account. Please try to give a good answer, for discussions, please use comments and please do remember to vote (login to vote)
toggle preview

powered by CNPROG