Using resoaance fluorescence the kinetics of NH (X 3~-) was studied in the pulsed vacuum UV photolysis of mixtures of NH3 and NO. The rate constant of the reaction NH + NO was determined to be (4.7 f 1.2) x lO_" cm3 m01ecuIe-~ ssl. in the course of an investigation of the kinetics of imino radicals we have recently studied the quenching of metastable NH and ND radicals in their (b Ix') states [ 1,2] . in the present paper we would like to describe a method to study rhe kinetics of ground state NH (X3x-) radicals. Kinetic data on reactions of NH (X3 I??) radicals is sparce. Only a few estimates on rate constants are reported which are based on experimental work such as those for the reactions with NH3 131, NH, 02, C3Hg 141, C2H4 [4,5], NO [6], I-IN, [7] and N2H4 [8] _ None of these rate constants have been obtained from more than one experiment. In the most direct studies, NH (X 3 xc-) has been generated either by electron bombardment or flash photolysis of NH, or HN, and was detected by time resolved absorption spectroscopy. With these techniques concentrations
of NH in the approximate range of 3 X tOI cms3 to 2 X 1Oi5 cmB3 were produced and lifetimes 71/z d 0.2 ms were usually observed. In the presence of NH, it was concluded that NH is removed efficiently by NH3 [3,9] and even more efficiently by NH 141.
The apparatus used in the present study consisted of a pulsed light source, a reaction chamber, an NH emission lamp and a resonance fluorescence detection system. A similar photolysis apparatus for the study of the kinetics of OH radicals has been described previously [IO] _ Vacuum W light pulses ~~~~~ = 1.5 ps) were generated by discharging a capacitor with a repetition frequency of about 0.2 Hz. NH (X3x;-)