The picosecond predissociation dynamics of vibronic levels of the ($) over tilde B and ($) over tilde C’ Rydberg states of ammonia have been investigated in real time by (2 + 1’) two-color pump-probe ionization in combination with photoelectron spectroscopy. The picosecond real-time results are in reasonable agreement with the results obtained from indirect methods using nanosecond excitation. These indirect methods include investigations of the peak intensities and the natural line widths of the rotational lines in the excitation spectra. The photoelectron spectra obtained for (2 + 1) ionization via the ($) over tilde B state in NH3 and ND3 are interpreted and shown to allow for an accurate determination of hitherto unknown vibrational frequencies in the ground state of NH3+ (ND3+). For the vl symmetric stretch a frequency of 0.404 +/- 0.0007 eV (0.303 +/- 0.007 eV) is found, while the frequency of the v(4) asymmetric bend vibration has been established as 0.197 +/- 0.007 eV (0.141 +/- 0.007 eV). The hydrogen atom fragment, which results from the predissociation of the ($) over tilde B and ($) over tilde C’ Rydberg states, has been detected in a two-color pump-probe experiment using nanosecond excitation.