The ultrafast dynamics of excited states in cerium oxide are investigated to access the early moments of polaron formation, which can influence the photocatalytic functionality of the material. UV transient absorbance spectra of photoexcited CeO₂ exhibit a bleaching of the band edge absorbance induced by the pump and a photoinduced absorbance feature assigned to Ce 4f → Ce 5d transitions. A blue shift of the spectral response of the photoinduced absorbance signal in the first picosecond after the pump excitation is attributed to the dynamical formation of small polarons with a characteristic time of 330 fs. A further important result of our work is that the combined use of steady-state and ultrafast transient absorption allows us to propose a revised value for the optical gap for ceria (E_og = 4 eV), significantly larger than usually reported.

中文翻译：

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小极化子的超快形成和CeO2中的光学间隙。

研究了氧化铈中激发态的超快动力学，以了解极化子形成的早期时刻，这会影响材料的光催化功能。光激发的CeO _2的紫外瞬态吸收光谱显示出由泵浦引起的能带边缘吸收率的漂白和分配给Ce 4f→Ce 5d跃迁的光致吸收特征。在泵浦激发之后的第一皮秒内，光诱导吸收信号的光谱响应的蓝移归因于动态形成的小极化子，其特征时间为330 fs。我们工作的另一个重要结果是，稳态和超快速瞬态吸收的结合使用使我们能够为二氧化铈的光学间隙提出修正值（E_og = 4 eV），比通常报道的要大得多。