Knowledge Bank

The first member of the sixth series in the spectrum of atomic hydrogen has been observed in the predicted position at $12.4\mu$. The source used is a water-cooled discharge tube drawing 640 ma at 5000 volts, this being the maximum energy consumption with the presently available power supply. The tube is fitted with a rocksalt window and exposed end-on. The optimum condition for maintaining an atomic hydrogen discharge as free as possible from the spectrum of $H2$ is realized by admitting water vapor through a Hopfield leak and pumping continuously. The pressure maintained is the lowest which will permit steady operation of the discharge. Under this condition the current is at maximum and the decrement between successive series the least. A Perkin-Elmer Model 12 spectrometer, with a rocksalt prism, a Hornig thermocouple as furnished with the early models, a Liston-Folb amplifier, and a Speedomax recorder were used in the observations. Reproductions of records, together with those of other hydrogen series, will be displayed. Relative intensities under conditions for maximum development of the series will be discussed.