dl914282

@swansont: Thanks for the answer. So, the stuff I wrote about Larmor precession and motion of magnetic moment vector is correct (at least as an approximation)? That's what I figured out from this paper: http://www.colorado.edu/physics/phys7550/phys7550_sp07/extras/Ramsey90_RMP.pdf It's for an assignment on Nobel prize in 1989. and atomic clocks. I needed to figure out Rabi's method in order to understand Ramsey's method, in order to understand cesium beam standard clock... I'm in 3rd semester of physics so it's kinda above my current knowledge of physics

Updated version (understanding): - Atoms originate from the source and pass through inhomogeneous field of magnet A (which selects those in lower energy state), then through region C in which a weak static field H0 exists, with field H1 rotating around it with frequency f, and then pass through another inhomogeneous field (magnet B, which selects those in HIGHER energy state) before reaching the detector. - In the static field Ho, nuclear magnetic moment vector rotates around static field vector Ho with Larmor frequency f0. - If f = f0 , in the static + rotating field, as viewed from H1's frame of reference, magnetic moment vector will rotate around H1 (animation), and this will cause the angle of magnetic moment with respect to H0 to continuously change. (pic) - If an atom flips its moment, it gets deflected differently, and corresponding decrease in intensity at detector is observed. - Frequency of radiation (of rotating field H1 ; f) is tuned so that there is maximum change in intensity at detector. animation of precession in rotating frame of reference: http://upload.wikimedia.org/wikipedia/commons/d/d8/Animated_Rotating_Frame.gif pic: http://www.quantiki.org/mediawiki/images/0/05/Precession.jpg Is this correct?

I'd like some help in understanding how Rabi's resonance method works. The figure bellow is the apparatus used. Molecules (or other particles) originate from source and travel through magnetic field of magnet A, then through collimator, and then are deflected by B magnet to detector. In the region of C magnet, a static field Ho exists and an additional rotating field H1, which precesses around H0. From what I understand, in a static magnetic field, nuclear magnetic moment vector will precess around the field vector with Larmor frequency. The angle between the magnetic moment and field vector remains constant, right? But what happens when the rotating field H1 is added? "If energy is absorbed by the nucleus, then the angle of precession will change. For a nucleus of spin 1/2, absorption of radiation "flips" the magnetic moment so that it opposes the applied field (the higher energy state)." http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/nmr1.htm Radiation is absorbed by nucleus if radiation's frequency matches nuclei's Larmor frequency? So, if the energy of an atom is changed, it gets deflected differently at magnet B and the detection signal changes. So, you can measure these states of nuclei if you tune the frequency of rotating field to Larmor frequency? Please correct any mistakes you may find. I'm sure there are many. Any help is appreciated. EDIT: After further investigation, I believe this animation shows what happens to the angular momentum (and thus magnetic moment) in the region C: http://en.wikipedia.org/wiki/Rotating_reference_frame#mediaviewer/File:Animated_Rotating_Frame.gif