Abstract A scheme is presented for differentiating a wavefunction with respect to polar angle coordinates using a fast Fourier transform (FFT) technique in the angular space, and which involves the same number of FFTs as for the well studied case of radial coordinates. This has been used to solve the time-dependent solution of the Schrödinger equation in Jacobi coordinates. The method is illustrated by calculating the energies of bound states and quasi-bound resonances in the HCO radical. The rotational population of the CO photoproduct arising from the predissociation of the first electronically excited state of HCO has been computed using an ab initio potential for the ground electronic state. The results are in good agreement with experiment.