Fig. 2: Spectral signatures of photogenerated charges on the femtosecond–nanosecond timescale.
From: Metal-centred states control carrier lifetimes in transition metal oxide photocatalysts
a–c, The transient absorption spectra for Fe2O3 (a), Co3O4 (b) and Cr2O3 (c) upon LMCT excitation (3.10 eV, 2.76 eV and 3.76 eV, respectively). d–f, The transient absorption spectra for Cr2O3 upon LF excitation (2.70 eV) (d). The transient absorption amplitudes are expressed as mΔA, where 1 mΔA = 10–3 ΔA (differential absorbance). The dashed black lines and dashed red lines indicate the transitions and bandgaps shown in Fig. 1a, respectively. The filled yellow and purple regions illustrate the shape of the broad and structured components discussed in the text, originating from direct carrier absorption (e) and the Stark effect (f), respectively. Note that the same number of photons absorbed was used for comparing LF and LMCT in Cr2O3. Any smaller sharp signals observed around 1.6 eV are probe light artefacts rather than real features.
