Gas spectrum tubes Containing 6 common gases for spectroscopic analysis. Gas content: H₂ , N₂ , He, Ar, Hg, Ne. Ideal for wavelength determination and introducing students to the spectra of the better known gases, these glass tubes are 10″ long, and the capillary portion is about 4″ long. The spectrum tube assemblies can be used in a variety of spectroscopic applications. When they are observed through a spectroscope the emission lines corresponding to the energy transition levels of the gaseous atoms or molecules will appear as distinct components. For use with Spectrum Tube Power Supply.