PREDISSOCIATION SUPPORTED HIGH-RESOLUTION VACUUM-ULTRAVIOLET ABSORPTION-SPECTROSCOPY OF EXCITED ELECTRONIC STATES OF NH3

Using monochromatic vacuum ultraviolet radiation generated by two-phot on resonant sum frequency mixing in a Mg-Kr mixture we have investigat ed the electronic transition of NH, in the 67 000-73 000 cm(-1) region by detecting the fluorescence from the predissociation fragments Of N H3. 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 ded uced. The predissociation in the ($) over tilde B (1)E'' state is foun d to be nearly independent of the rotational quantum numbers (J,K) wit hin one vibrational band. The linewidths of different vibronic compone nts of the ($) over tilde B (1)E'' state are measured. In addition, ot her absorption bands are presented including previously unobserved wea k absorption features.