TIME SYMMETRY - AN APPLICATION TO SHAPED PULSE EXCITATION OF SPIN-1 SYSTEMS

The role of time symmetry in the design of amplitude-modulated (shaped ) pulses for spin-1 excitation is examined. The quaternion calculus is used to calculate the quaternion elements (Euler-Rodrigues parameters ) of each shaped pulse. In this manner, it is shown how the simplicity and compactness of the Euler-Rodrigues parametrization can be used to significantly expedite a computer search for optimal time-symmetric s haped pulses. Theoretical and experimental tests of a new class of sym metric quadrupole-shaped (SQUASH) pulses identified by this procedure show a significant improvement in both excitation bandwidth and effici ency in comparison to the time-asymmetric QUASH shaped pulse previousl y identified. (C) 1998 Published by Elsevier Science Ltd.