Measurements of absolute density of ammonia in nitrogen–hydrogen mixture dc glow discharges were performed by employing photofragment translational spectroscopy associated with laser induced fluorescence (LIF) of the H ground state atoms. The dissociation energy of ammonia using the photolysis at 205 nm was determined to be (4.34±0.07) eV. The H atom LIF measurements were calibrated by vacuum ultraviolet absorption spectroscopy on the Lyman‐α (121 nm) line. The ammonia synthesized in the discharge has a maximum density of about 8×1012 cm−3 for a 75% H2–25% N2 mixture, a discharge current of 50 mA and a pressure of 2 Torr.