Laser induced fluorescence spectrum of ruthenium monoboride (RuB) in the visible region between 500 and 575 nm was studied. RuB molecule was produced by reacting laser ablated ruthenium atom with 0.5% diborane (B2H6) seeded in argon. Three transition bands of the [18.4] 2.5-X-2 Delta(5/2) transition were recorded and rotationally analyzed. The ground state symmetry and bond length, t(o), were determined to be X-2 Delta(5/2) state and 1.7099 angstrom, respectively, which is consistent with a (2)Delta(i) state predicted from electronic configuration using a molecular orbital energy level diagram. This work represents the first experimental investigation of the spectrum of the RuB molecule. (c) 2012 Elsevier B.V. All rights reserved.