Light-induced absorption changes by excitation of metastable states in Na-2[Fe(CN)(5)NO]2H(2)O single crystals

Abstract

The ground state and the light-induced metastable states of Na-2[Fe(CN)(5)NO].2H(2)O were investigated by polarized optical absorption spectroscopy on single crystals. An orbital level scheme is proposed for the ground state and the two metastable states SI and SII. Based on polarization analysis of the electronic transitions and density of states calculations using density functional theory (DFT), three electronic transitions were tentatively assigned to the calculated transitions of the orbital level scheme of SI and four to that of SII. Isosbestic points at 562 and 375 nm in the absorption spectra during the population of SI indicate that anions are transferred from the ground state into SI. No optical depopulation process from SI into the ground state is observed between 375 and 562 nm. An effective transfer from SI into SII can be performed by irradiation with light of wavelength above 770 or 910 nm and polarization of the light parallel to the c or a axis of the orthorhombic crystal, respectively.