Spin (1 Viewer)

[Haku]

i was reading a book, and also some notes and was confused now.

for spin does all proton spin one way while the neutrons spin the other? cause the book says when a atom with even number of protons and neutrons no angular momentum is present.

is that right?,

 

[rnitya_25]

huh?! .....ok, i haven't finished the whole course yet, but what the hell are you on about? lol sorry...curious, are you in the wrong thread?

 

[Jago]

He's in the right thread, this is in the MRI section.

What you have to consider is in a normal field, the protons face all different directions. Even in an aligned field, some protons are antiparallel.

 

[helper]

Each nucleon in a nucleus has a spin, Like electrons they fill up from the lowest energy level first. Also two nucleons can't have the same co-ordinates (including spin).
So if there are an even number of a nucleon type, then they will match up into pairs. As one will have an up spin and the other a down spin, the nucleus will not be magnetic.

If a nucleus has an overall spin, then it works as Jago said.

 

[Haku]

when u say nucleon do u mean proton? cause nucleon is the protons and neutrons in an atom, which = nucleus

 

[helper]

No I meant nucleon, meaning proton or neutron. Eg C-13. Has 6 Protons and 7 neutrons, so has a spin.

http://www.cis.rit.edu/htbooks/nmr/inside.htm has a description of spin mechanics but is a bit detailed

 

[Haku]

damn, knew shouldn;t of corrected you...lol.

so as long as the number of protons and neutrons differ there will always be spin right? would a question actually ask you for the amount of spin this nucleus have? or would it give u info.

another thingy, um it says the spin come in multiples of 1/2 either positive or negetive. but in the book it say they come in minimum multiples of 1/2[pi] ...confusion

thanks helper for making this clear.

just wondering what year did you do your hsc? you seem to know everything or double the amount of hsc material. do u do physics stuff at uni? thanks again for the help

 

[helper]

Quantum mechanics sure isn't my speciality. Actually, while it fascinates me, it makes my mind go in circles at times.
As long as there is an odd number of protons or neutrons there will be a spin. If there is an even number of nucleons overall, there can still be a spin.

The 1/2 or -1/2 is the quantum number. The 1/2{pi] is the amount of spin.

 

[HotShot]

yeah its like the earth spinning on its axis, magnetic field lines. nice how it works. its better than quanta and astro i mean they are so boring this is more practical and you can see it working.

 

[:daryl]

confused also

nucleon = proton and neutron..how come electrons are ignored

precession frequency is Larmor frequency rite?!

whats wid hydrogen nucleons having SOME protons spinning up and SOME spinning down...do they spin differently altough they r the same proton...(really confused on that 1*)

you can only have a magnetic field produced if the net spin = 0 rite?!

whats with attemp to re-orientate/flip if a strong magnetic field is applied although it doesnt fully allign, resulting to precession...pls explain..

thanx

 

[Haku]

nucleon = proton and neutron..how come electrons are ignored

precession frequency is Larmor frequency rite?!

whats wid hydrogen nucleons having SOME protons spinning up and SOME spinning down...do they spin differently altough they r the same proton...(really confused on that 1*)

you can only have a magnetic field produced if the net spin = 0 rite?!

whats with attemp to re-orientate/flip if a strong magnetic field is applied although it doesnt fully allign, resulting to precession...pls explain..

thanx

yes the precession frequency is the larmor frequency.
H nuclei by haveing 1 proton alow it to have a net spin thats not 0. this is because there is no other protons to spin the other or to cancel out each others magnetic fields.
like normal magnite it can face any way it want if there were not external magnetic field to line up all the poles. Using the right hand grip rule u can figure our the direction of spin or the north pole which is the side the thumb points to.

when net spin is 0 there is no magnetic, u just need to know they come in 1/2.
when external mag field is present it will always precess around a field line, this is either parallel or anti parallel. and it is done at the larmor frequency.