A study of a sparkdischarge in hydrogen at atmospheric pressure

A spark expanded by a magnet was assessed as a low temperature atmospheric pressure source of hydrogen atoms. Calorimeters with masses from less than a gram to about 1 kg were used to measure the hydrogen atom flux and its distribution in a discharge tube of about 200 cc volume in which a spark of 0.3 J was repeated 100 times a second in hydrogen at atmospheric pressure. Spectroscopic observations and reactions with MoO₃ were used to confirm the presence of hydrogen atoms. The results showed that the expanded spark discharge at atmospheric pressure is a simple, inexpensive and relatively efficient means of producing hydrogen atoms. 30% to 40% of the spark energy was found to go into the production of hydrogen atoms corresponding to fluxes of around 3 × 10¹⁷ hydrogen atoms per discharge. Atoms were found to reach unexpectedly large distances from the discharge, e.g. 10¹⁷ atoms per discharge were found 40 mm away.