A new method has been devised to determine the molar absorption coefficient of short-lived photochemical species formed by laser irradiation. The technique consists of a first pump excitation pulse that significantly modifies the concentration of the initial species in its ground state, enough that the variation of the absorbance at maximum absorption of the formed species depends on the initial species concentration. A new absorbance variation is created by a second excitation pulse occurring with a time delay after the first pulse that is small compared to the lifetime of the formed species. The molar absorption coefficient is calculated using the ratio of these two variations in absorbance, assuming that the initial species does not absorb in the spectral range where the absorption variation of the formed species is observed.
已经设计出一种新方法来确定激光照射形成的短寿命光
化学物质的摩尔吸收系数。该技术包括一个第一泵激发脉冲,该脉冲显著改变初始物质在基态下的浓度,足以使所形成物质的吸光度在最大吸收时的变化取决于初始物质的浓度。第二激发脉冲在第一脉冲之后发生,与所形成物质的寿命相比,时间延迟很小,从而产生新的吸光度变化。摩尔吸收系数是通过这两个吸光度变化的比率计算得出的,前提是初始物质在所形成物质的吸光度变化被观察到的光谱范围内不吸收。