Bloch–Siegert shift
From Wikipedia, the free encyclopedia
The Bloch–Siegert shift is a phenomenon in quantum physics that becomes important for driven two-level systems when the driving gets strong (e.g. atoms driven by a strong laser drive or nuclear spins in NMR, driven by a strong oscillating magnetic field).
This article provides insufficient context for those unfamiliar with the subject. (October 2020) |
When the rotating-wave approximation (RWA) is invoked, the resonance between the driving field and a pseudospin occurs when the field frequency is identical to the spin's transition frequency . The RWA is, however, an approximation. In 1940 Felix Bloch and Arnold Siegert showed that the dropped parts oscillating rapidly can give rise to a shift in the true resonance frequency of the dipoles.
The Bloch–Siegert shift has been used for practical purposes in both NMR and MRI, including power calibration,[1] image encoding,[2] and magnetic field mapping.[3]