Abstract: Under the condition of finite pulse width, using a vector model and computer simulation, the present paper proposed a composite 180° pulse:45°_x 112. 5°_y 45°_x, for uniform population inversion in the central transition of spin-3/2 nuclear systems. And the performance of population inversion of the composite 180° pulse was obtained by numerical calculation and confirmed by experimental results of ²³Na NMR spectra in Na₂SO₄ powder sample.

Key words: Powder sample, Central transition of quadrupolar nucleus, Population inversion