Abstract The emission band spectrum of gallium monobromide in the region λ3700–λ3400 A excited in a radio-frequency discharge is photographed in the first-order dispersion (1.25 A/mm) of a 21 ft concave grating spectrograph. The spectrograms taken under high resolution reveal the presence of about 100 new bands which are assigned to the two subsystems (A and B) of a 3Π0,1−X1Σ transition reported earlier in absorption. The analysis states that the vibrational quantum numbers of some of the bands are to be increased by one unit. The vibrational quantum formulae derived for the band heads of these two systems of the more abundant 69Ga79Br molecule are as follows: subsystem A: ν v′,v″ = 28 162.53 + 275.75(v′ + 1 2 ) − 2.25(v′ + 1 2 ) 2 − 266.9(v″ + 1 2 ) + 0.83(v″ + 1 2 ) 2 ; subsystem B: ν v′,v″ = 28 532.92 + 274.6(v′ + 1 2 ) − 2.58(v′ + 1 2 ) 2 − 266.9(v″ + 1 2 ) + 0.89(v″ + 1 2 ) 2 . The analysis of these two subsystems is further suported by the study of isotopic shifts due to the isotopic species of gallium and bromine.