Isotope shifts in the N2(C3Πu-B3Πg) second positive system

Wavelength differences between corresponding ¹⁴N₂ and ¹⁴N¹⁵N bandheads were measured in spectra emitted from microwave-excited low-pressure discharge tubes containing ammonia. The spectra were mainly recorded photographically using a large quartz-prism spectrograph (Hilger and Watts). The measured isotopic bandhead shifts were shown to be in good agreement with calculated values, based on molecular constants for ¹⁴N¹⁵N derived from those for ¹⁴N₂ by using the Dunham isotope relations. Shifts are reported for 15 bandheads.