Figure 1. The bromine spectrum in the vicinity of Hα (6563 Å).

Exposure (b) was made with an electrodeless discharge tube containing bromine vapor excited by a microwave diathermy unit. Exposure (d) is of bromine excited by a high voltage ring discharge apparatus that enhanced Br II. The other exposures are of thorium, which served as secondary standards. Hα occurs only in the middle thorium exposure (c).