A diode laser has been used to measure the absorption spectrum of the ν3 band of MoF 6 (740-750 cm -1). A rich Q-branch spectrum was observed with natural-abundance MoF 6 and with isotopically pure samples of 92MoF 6, 96MoF 6, and 100MoF 6. Q-Branch subbandheads were observed experimentally, their absolute frequencies were determined, and the spectra were compared to computer-generated simulations. From the comparison to spectral simulations, the band-center frequencies, the effective perturbations to the rotational constants, and the octahedral splitting constants for the three isotopes have been determined. A number of tests were conducted using a gas-dynamic expansion to cool the MoF 6 in order to assess the feasibility of laser isotope separation of molybdenum.