VACUUM-ULTRAVIOLET PHOTOLYSIS OF N2H2 - GENERATION OF NH FRAGMENTS

The photodissociation of the double bond in HN=NH yielding electronica lly excited NH(A 3PI) and ground state NH(X 3SIGMA-) radicals has been studied in the vacuum-ultraviolet above 105 nm. Fragment excitation s pectra were taken using tunable synchrotron radiation as the photolysi s light source. The excited radicals were detected by their triplet em ission to the ground state. A very crude estimate results in 10%, 20%, and 70% of the excess energy to be channeled into fragment vibration, rotation, and translation, respectively, at the Kr resonance line at 123.6 nm. This energy distribution supports a repulsive process with a lmost equal rotation in the two NH fragments and vibration caused by l engthening all bonds during the N=N bond breaking. An upper limit for the energy necessary to break the double bond is measured to be 510.7 +/- 1.2 kJ mol-1. This value yields DELTA(f)H-0(0)(N2H2) greater-than- or-equal-to 204.1 +/- 2.2 kJ mol-1.