The transmission coefficient of a 30-nm-thick silver film for single visible laser pulses with a wavelength of 515 nm and a duration of 300 fs decreases steadily with an increase in the peak intensity of the pulses, which means that the absorption coefficient of the material increases accordingly. Taking into account the high initial density of free s electrons in the material, the heating of the electron gas corresponds to a monotonic increase in the absorption coefficient of silver as a function of the electron temperature. At the same time, photoinjection of additional nonequilibrium free carriers (~10²² cm^–3) caused by multiphoton d–s interband transitions from quasibound d states lying below the Fermi level can also be successfully invoked to qualitatively explain the dependence of the absorption coefficient on the peak intensity of the laser pulses. It is shown by the example of silver that, in order to describe changes in the optical properties of transition metals during an ultrashort excitation laser pulse, one has to take into account both the interband photoinjection of additional carriers and the characteristics of the resulting nonequilibrium states of the electron gas. The relative contributions from these two factors are largely determined by the relation between the width of the band gap between the Fermi level in the s band and the top of the d bands and the photon energy.

对于波长为515 nm，持续时间为300 fs的单个可见激光脉冲，厚度为30 nm的银膜的透射系数随着脉冲的峰值强度的增加而稳步下降，这意味着材料会相应增加。考虑到游离的高的初始密度小号电子在材料中，电子气对应的加热到银中的吸收系数的单调增加作为电子温度的函数。同时，由多光子d – s从准结合d的带间跃迁引起的其他非平衡自由载流子（〜10 ²² cm ^–3）的光注入费米能级以下的状态也可以成功地调用，以定性地解释吸收系数对激光脉冲峰值强度的依赖性。以银为例可以看出，为了描述过渡金属在超短激发激光脉冲过程中的光学特性变化，必须同时考虑附加载带的带间光注入和所得非平衡态的特性。电子气。这两个因素的相对贡献在很大程度上取决于s波段和d波段顶部的费米能级之间的带隙宽度与光子能量之间的关系。