PHOTOIONIZATION MASS-SPECTROMETRIC STUDY OF N2H2 AND N2H3-N-H, N=N BOND-ENERGIES AND PROTON AFFINITY OF N2

The photoion yield curves of N2H2+, N2H+, and H2+ from N2H2 have been studied by photoionization mass spectrometry. The adiabatic ionization potential of N2H2 determined (9.589 +/- 0.007 eV) is in excellent agreement with that obtained by photoelectron spectroscopy (PES). The appearance potential of N2H+ (10.954 +/- 0.019 eV at 0 K) is in good agreement with earlier electron impact measurements. The appearance potential of H-2+ (< 13.52(6) +/- 0.03; probably less-than-or-equal-to 13.403 +/- 0.036 eV, at 0 K) leads to DELTA-H(fo)0 (N2H2) > 43.8 +/- 0.7; probably greater-than-or-equal-to 46.6 +/- 0.8 kcal/mol. Consequently, proton affinity (PA) (N2) < 121.8 +/- 0.8; probably less-than-or-equal-to 119.0 +/- 0.9 kcal/mol, which is in good agreement with results from proton transfer experiments and with most ab initio calculations. The N = N "double bond" energy determined from N2H2 --> 2NH is < 126.6 +/- 1.0; probably less-than-or-equal-to 123.8 +/- 1.1 kcal/mol. The adiabatic ionization potential of N2H3 is found to be 7.61 +/- 0.01 eV. This observation leads to D0 (H2NNH-H) = 80.8 +/- 0.3 kcal/mol, and D0(HNNH-H) congruent-to 43.8 +/- 1.1 kcal/mol.