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Key points: • TG in optical range has been used to study coherent phonons and thermal transport • To move to nano-scale need to reduce grating period and hence the wavelength • LCLS provides unique opportunity –> coherence and time resolution • Experimental requirements –> split and delay of pump and probe –> generation of overlapping beams • Generalized non-linear X-ray spectroscopy X-ray four-wave mixing: Transient grating measurements of nano-scale thermo-elastic responses F. Hofmann , K.A. Nelson Roseker et al. Optics Letters 34 (12) 2009 X-ray pump-probe splitting Transient grating Johnson et al. J. Appl. Phys. 110, 113513 (2011) sample x-ray gratings signal Transient grating generation Heilmann et al. Optics Express 16, 8658 (2008) Ti film on Si substrate, 0.76μm grating period Rogers et al. Annu. Rev. Mater. Sci. Decane with alumina nanoparticles Schmidt et al. J. App. Phys. 103, Coherent phonons & thermal grating decay
