RF pulse designed to rotate the macroscopic magnetization vector 90° in space as referred to the rotating frame of reference, usually about an axis at right angles to the main magnetic field. If the spins are initially aligned with the magnetic field, this pulse will produce transverse magnetization and a FID. Also called P/2 Pulse.

(X') Dimension in the rotating frame of reference in the plane at right angles to the direction of the static magnetic field (B0 or H0), z; commonly defined to be in the direction of the magnetic vector of the exciting RF field (B1).

(Y') Dimension in the rotating frame of reference in the plane orthogonal (at right angles) to the direction of the static magnetic field (B0 and H0), z, and orthogonal to the other dimension in the plane, x'.

(MZ) Dimension in the direction of the static magnetic field (B0 and H0), in both the stationary and rotating frames of reference.