Electronic transition spectrum of iridium monoboride in the spectral region between 400 and 545 nm has been recorded and analyzed using laser vaporization/reaction free jet expansion source and laser induced fluorescence spectroscopy. Thirteen vibrational bands belonging to four electronic transitions, namely the [18.8](3) Delta(3) - X-3 Delta(3), [21.1](3)phi(4) -X-3 Delta(3), [22.8](3)phi(3) -X-3 Delta(3), and [22.4](1)phi(3) -a(1)Delta(2) transitions, have been identified and rotationally analyzed. Spectra of all four isotopic molecules were observed. (C) 2010 Elsevier B.V. All rights reserved.