A method is devised better to resolve the subbands of the ground vibronic band in the mass-analyzed threshold ionization (MATI) spectrum of CD(3)I. By selective photodissociation of CD(3)I(+) in these subbands, high-resolution spectra for the A(2)A(1)<--X(2)E(3/2) transition are recorded. Spectral analysis confirms our previous suggestion that these subbands are due to cations in different rotational K states; this demonstrates the capability of MATI to generate rovibronically selected ion beams. By using the rotational constants of CH(3)I(+) and CD(3)I(+) obtained by spectral analysis, the zero-point-level geometries of the cations in the X(2)E(3/2) and A(2)A(1) states are determined. To the best of our knowledge, this is the first time that the capability of MATI-PD to determine the geometry of a gas-phase polyatomic cation in an excited electronic state is demonstrated.