We consider the use of adiabatic half-passage pulses (AHP) for the uniform excitation of highly non-equilibrium spin-systems such as spin-exchange optically pumped (SEOP) Xe-129. The method simplifies a number of problems that are encountered for these systems, notably the non-renewable nature of the magnetization, the need for accurate pulse calibration and the influence of radiation damping. This is shown to be a straightforward method for achieving the maximum obtainable signal and thereby for measuring the degree of polarization on a 1.5 T clinical MRI scanner. (c) 2005 Elsevier B.V. All rights reserved.