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3.2.2 Magnetic Field in general direction Larmor frequencies: Hamiltonian: In matrix representation 

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1 3.2.2 Magnetic Field in general direction Larmor frequencies: Hamiltonian: In matrix representation 

2 Rewriting the Hamiltonian:    Characteristic equation:

3 Eigenstates: Spin Flip: or Initial state Time evolved state z B

4  z BProbability of a spin flip

5 Sinceand Rabi Formula t z B

6 t     (a) (b) t     (c) z B z B B z

7 The most general initial state: In matrix formalism 0 T       T

8 Probability for measuring the spin projection along the z-axis: Probability for measuring the spin projection along the x-axis:

9 3.4 Magnetic Resonance Magnetic Resonance Image showing a vertical cross section through a human head. Modern 3 tesla clinical MRI scanner. Magnetic Resonance Imaging (MRI) http://en.wikipedia.org/wiki/Magnetic_resonance_imaging

10  Uniform magnetic field: Additional rotating magnetic field: Total magnetic field: Time dependent Hamiltonian: x y z

11 Matrix representation of the Hamiltonian: Schrödinger Equation :

12 State vector as viewed from the rotation frame: Schrödinger Equation becomes:

13 where In the rotating frame the Hamiltonian is time independent!!

14 Rabi Formula When Rabi Formula with   

15 Rabi flopping equation where Generalized Rabi frequency  When   (resonance condition),  Rabi frequency.

16 Amplitude of the spin flip probability: Lorentzian curve   Magnetic resonance curve   FWHM emissionabsorptionemission absorption t   Time dependent spin flip probability:


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