Laser induced fluorescence spectrum of boron carbide (BC) between 490 and 560 nm has been recorded and analyzed. Gas-phase BC molecule was produced by the reaction of diborane and methane in the presence of magnesium atom from laser ablation process. The (0, 0), (1, 0), and (2, 0) bands of the B-4 Sigma - X-4 Sigma transition were rotationally analyzed. Spectra of both isotopes: (BC)-B-10 and (BC)-B-11 were analyzed. Equilibrium molecular constants for the B-4 Sigma and the X-4 Sigma states for both isotopes were determined. (C) 2011 Elsevier B.V. All rights reserved.