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visits member for 2 years, 6 months
seen Feb 16 at 19:28

Jan
21
awarded  Popular Question
Oct
16
awarded  Popular Question
Oct
13
accepted Have $2s_{1/2}$ and $2p_{1/2}$ the same energy?
Oct
11
comment Have $2s_{1/2}$ and $2p_{1/2}$ the same energy?
@JohnRennie from lecture notes.. it is referring to the hydrogen...
Oct
11
asked Have $2s_{1/2}$ and $2p_{1/2}$ the same energy?
Oct
10
comment About Nuclear magnetic resonance
and what about frequency of the pulse? can it have any value in the range of RF?
Oct
10
comment About Nuclear magnetic resonance
(...continue) must be applied after spins relaxation... I have understood that the spins relaxation starts when I turn off the pulse... And that the pulse is so strong that forces all the nuclei to have the same larmor frequency... isn't it? The only thing that the pulse does is to move the net magnetization away from z-axes and allow some nuclei to make the transition?
Oct
10
comment About Nuclear magnetic resonance
Mmmh... wait! I'm loosing! :D I have understand that I apply a static magnetic field to polarize the spins. Then I want the NMR signal, so I have to perturb the system. I employ an RF pulse very intense and for a very small time interval. Some nuclei make the transition and the net magnetization feels 1) the static field and 2)this new field. The result is a spiral motion that leaves the z-axes. The net magnetization stops its motion at the flip angle and I have the transverse magnetization that I needed. (please, tell me I have made mistakes). Now, I haven't understand why the pulse..
Oct
10
comment About Nuclear magnetic resonance
thanks George. It is clear now! Talking with Floris, a new doubt comes out: does the pulse modify the larmor frequency of the nuclei or not? If not.. how can the pulse force all the atoms to be in phase? Many thanks again!
Oct
9
comment About Nuclear magnetic resonance
(I can't understand why the magnetization induces current)
Oct
9
comment About Nuclear magnetic resonance
Hi George, I have a question (I ask you because you work with NMR apparatus.. I hope not to disturb you!). I haven't understood why "As transverse magnetization rotates about the Z axis, it will induce a current in a coil of wire located around the X axis".. could you help me? Many thanks again!
Oct
2
comment About Nuclear magnetic resonance
Very interesting! Thanks!
Oct
2
comment About Nuclear magnetic resonance
Thanks for you answer! But I'm not sure to have correctly understood what you said about T1. I have understood that after a time T1, the Z-component of the net magnetization, is equal to 63% of its value at the equilibrium. Does it indicate also the time that the spins take to align with the external field?
Oct
2
accepted About Nuclear magnetic resonance
Oct
1
asked About Nuclear magnetic resonance
Sep
16
accepted Problem with shell model and magnetic moment of Lithium-6
Sep
16
comment Potential energy of a spring
@ROIMaison I haven't solved the problem... I'm sorry
Jul
2
awarded  Curious
Jun
28
accepted Totally antisymetric wavefunction: clarification about terminology
Jun
28
awarded  Promoter