In the present study, the possibility of photochemical separation of the Rb isotopes was demonstrated using the Rb* + CH3Cl/CF3Cl reactions and the isotope light filtration technique. The ratio between the TOF MS peaks corresponding to the (RbCl+)-Rb-85-Cl-35, (RbCl+)-Rb-87-Cl-35 + (RbCl+)-Rb-85-Cl-37 and (RbCl+)-Rb-87-Cl-37 reaction product ions was found to change from 7.7:5.6:1.0 for the unfiltered excitation radiation to 1.8:3.5:1.0 for the filtered radiation. (C) 2003 Elsevier B.V. All rights reserved.