Differential Scanning Calorimetry measurements on irradiated Cl-3[Ru(NH3)(5)NO]H2O reveal the existence of two light-induced long-lived metastable states SI, SII. Irradiation with light in the spectral range 400-500 nm leads to the excitation of SI. For the first time we report experimental evidence for the state SII in this compound, which can be excited by transferring SI into SII with irradiation of light in the spectral range 1000-1200 nm. The excitation and transfer of the metastable states is described and the exponential decays are evaluated according to Arrhenius' law yielding activation energies of E-A(SI) = 0.73(3) eV, E-A(SII) = 0.66(3) eV and frequency factors of Z(SI)= 1 x 10(12) s(-1), Z(SII) = 5 x 10(12) s(-1). (C) 2004 Elsevier B.V. All rights reserved.