Investigation of the metastable state of Na2[Fe(CN)5NO] · 2H2O by optical spectroscopy. II The electronic spectra of the ground and metastable states

The absorption spectra of Na2[Fe(CN)5NO] · 2H2O were measured in the visible region in the range of 3400–7000 A. In the metastable state, an additional absorption band in the long wavelength range is observed and the transition 2 b 2 (d xy )→ 7 e(π ∗ −NO ) becomes weaker in the excited state indicating a population of the π∗(NO)-orbital. The laser excited emission spectrum shows a broad luminescence beginning at the excitation line λ = 5145 A ( 19,436 cm -1 ) with a maximum at about 6250 A (16,000 cm-1). A strong sharp luminescence at about 7836 A is registered and may be assigned to a transition 3b1(dx2−y2) or 5a1(dz2) to the antibonding π∗(NO)- orbital. Further the broad luminescence is superimposed by a series of sharp spikes. These sharp spikes can also be observed for several days, when the laser is switched off, and are depending on the crystal orientation.