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The spin-echo effect was discovered by Erwin Hahn when he applied two successive 90° pulses separated by short time period, but detected a signal, the echo, when no pulse was applied. This phenomenon of spin echo was explained by Erwin Hahn in his 1950 paper, [ 5 ] and further developed by Carr and Purcell who pointed out the advantages of ...
Neutron spin echo is a time-of-flight technique. Concerning the neutron spins it has a strong analogy to the so-called Hahn echo, [13] well known in the field of NMR.In both cases the loss of polarization (magnetization) due to dephasing of the spins in time is restored by an effective time reversal operation, that leads to a restitution of polarization (rephasing).
The classical NSE technique (Figure 1. a)), relies upon the Lamor precession the neutron spin undergoes, while flying through static magnetic fields.Several other NSE schemes exist however, which employ resonant spin flips in a magnetic RF-field to achieve the same effect on the neutron, such as neutron resonant spin echo (NRSE) and modulation of intensity by zero effort (MIEZE).
Spin echo animation showing the response of electron spins (red arrows) in the blue Bloch sphere to the green pulse sequence. Pulsed electron paramagnetic resonance (EPR) is an electron paramagnetic resonance technique that involves the alignment of the net magnetization vector of the electron spins in a constant magnetic field.
The spin echo is a 90° pulse followed by a 180° pulse after a time period τ and is applied on the proton, the sensitive nucleus (designated, perhaps counter-intuitively, as the I spin, while the insensitive nucleus is the S spin; note, however, that the original paper on INEPT used the opposite designations). [1] Spin Echo
Spin echo small angle neutron scattering (SESANS) measures structures from around 20 to 2000 nm in size. The information is presented as a real-space (similar to g(r)) as opposed to a reciprocal space (q(r)) mapping. This can simplify the interpretation for some systems. [1]
[6] [7] [8] In spin systems in particular, commonly used protocols for dynamical decoupling include the Carr-Purcell and the Carr-Purcell-Meiboom-Gill (CPMG) schemes. [9] [10] They are based on the Hahn spin echo technique of applying periodic pulses to enable refocusing and hence extend the coherence times of qubits.
Without fat suppression techniques, fat and fluid will have similar signal intensities on fast spin-echo sequences. [58] Techniques to suppress fat on MRI mainly include: [59] Identifying fat by the chemical shift of its atoms, causing different time-dependent phase shifts compared to water.