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The Larmor frequency is important in NMR spectroscopy. The gyromagnetic ratios, which give the Larmor frequencies at a given magnetic field strength, have been measured and tabulated. [3] Crucially, the Larmor frequency is independent of the polar angle between the applied magnetic field and the magnetic moment direction.
The geomagnetic field strength and hence precession frequency varies with location and time. Larmor precession frequency = magnetogyric ratio x magnetic field Proton magnetogyric ratio = 42.576 Hz/μT (also written 42.576 MHz/T or 0.042576 Hz/nT) Earth's magnetic field: 30 μT near Equator to 60 μT near Poles, around 50 μT at mid-latitudes.
The detection of the NMR signal during or after the RF pulse, due to the voltage induced in a detection coil by precession of the nuclear spins around B 0. After an RF pulse, precession usually occurs with the nuclei's Larmor frequency and, in itself, does not involve transitions between spin states or energy levels. [1]
These procedures rely on the fact that bulk magnetization due to nuclear spins precess in a magnetic field at a rate called the Larmor frequency, which is simply the product of the gyromagnetic ratio with the magnetic field strength. With this phenomenon, the sign of γ determines the sense (clockwise vs counterclockwise) of precession.
The power is absorbed by the precessing magnetization (Larmor precession) of the material and lost as heat. For this coupling to occur, the frequency of the incident wave must be equal to the precession frequency of the magnetization (Larmor frequency) and the polarization of the wave must match the orientation of the magnetization.
If a horizontal rotating field , angular frequency of rotation is applied in the region between poles of magnet 2, produced by oscillating current in circular coils then there is a probability for the atoms passing through there from one spin state to another (= + / > / and vice versa), when = , Larmor frequency of precession of magnetic moment ...
These g-factors may be multiplied by 7.622 593 285 (47) MHz/T, [7] which is the nuclear magneton divided by the Planck constant, to yield Larmor frequencies (in MHz/T). If divided instead by the reduced Planck constant, which is 2π less, a gyromagnetic ratio expressed in radians is obtained, which is greater by a factor of 2π.
In the frame rotating at the Larmor frequency, the effective field experienced by the spins is in the transverse plane. Observing the spins in this frame shows spins precessing about B effective at a frequency proportional to | |. If the RF pulse is applied for a time shorter than the period of this precession, one can engineer the flip-angle ...