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. Author manuscript; available in PMC: 2012 Aug 14.
Published in final edited form as: Nat Photonics. 2012 Jan 15;6(2):111–114. doi: 10.1038/nphoton.2011.327

Figure 3. Absorption factor (μ(λ)L = –ln(T)) versus time delay.

Figure 3

μ(λ )L is the product of the absorption coefficient and the thickness, and the transmitted fraction is described by T = (1 – R)exp(–μx). Reflectivity R is calculated from the Fresnel relations and the GaAs dielectric constants. Any time dependence of R is assumed to be small and has been omitted. a, Laser beam transmitted fraction T (without X-rays) versus wavelength from below-gap (900 nm) to above-gap (850 nm) values. b, Exponential factor μ(λ )L for the GaAs specimen versus time delay for wavelengths of 850–900 nm. Note that the absorption factor profile approximates the Gaussian profile of the X-ray pulses for sub-gap wavelengths, consistent with the short-lived states induced by the X-rays (see text).