7: Lecture 7: The Radiofrequency Hamiltonian and the Rotating Frame
-
Published:13 Jun 2022
-
Special Collection: RSC eTextbook CollectionProduct Type: Textbooks
Lectures On Spin Dynamics: The Theoretical Minimum, The Royal Society of Chemistry, 2022, pp. 87-96.
Download citation file:
In this lecture, I introduce the radiofrequency Hamiltonian for radiofrequency pulses. These are largely used in NMR spectroscopy and MRI to interact with nuclear spins. Given the oscillating nature of the radiofrequency radiation, such a Hamiltonian has a time dependence that may complicate the spin dynamics. To remove such a time dependence, I use the interaction frame transformation introduced in Lecture 5 to define a rotating frame. I then discuss the effects of on- and off-resonance radiofrequency pulses and calculate the magnitude of the Bloch–Siegert shift generated by a counter-rotating term in the radiofrequency Hamiltonian.