Shock-tube measurement of the dissociation energy of NH using absolute band intensities

The NH radical has been observed spectroscopically in reflected shocks through nitrogen-hydrogen-krypton and ammonia-krypton mixtures. The (0, 0) band of the NH 3 II- 3 Σ - system was photographed in absorption under high dispersion. From a knowledge of the temperature and partial pressures in the equilibrium region behind the reflected shock and the rotational line strengths, a band f value was deduced as a function of dissociation energy. Comparison with independently determined f values based on measurements of radiation lifetimes leads to the value D (NH) = 3 21 ± 0 16 eV. Experimental scatter and uncertainty in thermodynamic data have been included in the error quoted. Other sources of error are discussed.