Stark-swept transient hole burning and resonant luminescence line narrowing in [Zn(2,2′-bipyridine) 3](ClO 4) 2:Ru(II)

Abstract

Resonant luminescence line narrowing and Stark-swept transient hole-burning experiments were performed in the electronic origins of the lowest excited states of the title material. The energies of the two lowest excited states are well correlated. No fine structure was observed in the range 300 MHz–30 GHz for the resonantly and non-resonantly narrowed origin II and I, respectively. This is at variance with the interpretation of ODMR experiments. At 4.2 K an upper limit of ≈ 25 MHz is deduced for the homogeneous line width of origin II. A large pseudo-Stark splitting of the origins is observed corresponding to |Δμ| ≈ 5.5 D. This value is used to calibrate Stark-swept transient hole-burning experiments which needed ± 33 V/cm to measure the entire hole shape. A homogeneous line width of 14 ± 2 MHz is found for origin II at 1.5 K. The large Stark effect is the first direct evidence for the charge-transfer character of the lowest excited states in [Ru(bpy) 3] 2+. The results are consistent with the localized nature of the lowest excited states.