Using monochromatic vacuum ultraviolet radiation generated by two-photon resonant sum frequency mixing in a Mg-Kr mixture we have investigated the electronic transition of NH, in the 67 000-73 000 cm(-1) region by detecting the fluorescence from the predissociation fragments Of NH3. The spectrum is simplified using a pulsed molecular beam. Vibronic bands of the B (1)E" (2(9), 2(10), 2(11), 2(12), 2(7)3(1), 2(8)3(1)) state are clearly identified and relevant molecular constants are deduced. The predissociation in the ($) over tilde B (1)E" state is found to be nearly independent of the rotational quantum numbers (J,K) within one vibrational band. The linewidths of different vibronic components of the ($) over tilde B (1)E" state are measured. In addition, other absorption bands are presented including previously unobserved weak absorption features.