Astronomers have now observed the radio emission from the neutral hydrogen gas (HI) in a nearby galaxy. Hydrogen gas emits radio emission in a spectral line at a very specific frequency of 1420 MHz.

On the spectrum of hydrogen -- On the series spectra of the elements -- The structure of the atom and the physical and chemical properties of the elements https ...

WHILE making experiments on the apparent production of neon and helium during electric discharges, I have noticed an effect which may be of interest to spectroscopists. A powerful oscillatory ...

Balloons filled with hydrogen and containing metal salts are ignited. When the balloon explodes, the characteristically colored flame for that metal is seen. This is best performed outside or in a ...