|dc.description.abstract||The first recognized preparation of hydrogen atoms in the gas phase was reported by Langmuir(1,2,3,4) in 1912 in a classical series of experiments on hot filaments. He found that the rate at which energy was lost from wires heated in hydrogen increased abnormally above 2100oK. This he explained by assuming that the hydrogen was dissociated into atoms. Many other experiments (5) confirmed this.
The next important preparation of atomic hydrogen was that of Wood. (6,7) In attempting to photograph additional lines of the Balmer spectrum of hydrogen, some interesting characteristics of atomic hydrogen were noted. It was observed that the free atoms had a relatively long life, of the order of 0.2 seconds at a pressure of 1 mm. of mercury, and could thus be pumped for an appreciable distance after leaving the discharge. Bonhoeffer(8,9) modified Wood's apparatus and used it to investigate the chemical properties of hydrogen atoms.
In recent years much attention has been directed to this photochemical dissociation of the hydrogen molecule: H2 + hV ¨ 2H||en_US