DOI: 10.5061/dryad.7sqv9s4z8
title: Evidence for phonon hardening in laser excited gold using x-ray diffraction at a hard x-ray free electron laser

description: Studies of laser-heated materials on femtosecond timescales have shown
 that the interatomic potential can be perturbed at sufficiently high laser
 intensities. For gold, it has been postulated to undergo a strong
 stiffening leading to an increase of the phonon energies, known as phonon
 hardening. Despite efforts to investigate this behavior, only measurements
 at low absorbed energy density have been performed, for which the
 interpretation of the experimental data remains ambiguous. By using in
 situ single-shot x-ray diffraction at a hard x-ray free electron laser,
 the evolution of diffraction line intensities of laser-excited Au to a
 higher energy density provides evidence for phonon-hardening.
description: The X-ray diffraction data were collected at the LCLS using an
 ePix10k detector. The detector was calibrated using a CeO2 calibrant. The
 orientation of the detector was then determined using the open source
 software Dioptas. The data were then corrected for polarization (the LCLS
 beam was vertically polarized). The edges of each detector tile were
 masked. The details about the extraction of the normalized intensity is
 found in the Materials and Methods of the manuscript.
 For timing between the optical laser pulse and the X-ray pulse,
 we used the time tool system available at MEC. The extraction of the
 relative timing, determination of the absolute timing, and timing
 uncertainties can be found in the Materials and Methods of the
 manuscript.
description: No particular software is needed to open the data files. We have
 used Python for the data analysis.
description: ## Evidence for phonon hardening in laser excited gold using x-ray
 diffraction at a hard x-ray free electron laser -- LCLS LW5919 This
 dataset contains the raw images used in the analysis for the manuscript
 entitles "Evidence for phonon hardening in laser excited gold using
 x-ray diffraction (XRD) at a hard x-ray free electron laser". The
 experiment was performed at the Matter in Extreme Conditions (MEC)
 endstation at the Linac Coherent Light Source (LCLS) at SLAC National
 Accelerator Laboratory. We are including the raw images for the X-ray
 diffraction pattern and the images collected using the timetool available
 at MEC. Further details can be found in the Materials and Methods of the
 main manuscript. ## Description of the data and file structure We are
 uploading a folder containing the XRD images named "XRD_dataset"
 and one folder with the timetool images named
 "timetool_dataset". Within each folder, we have separated the
 data in different sub-folders for each run collected during the
 experiment. Each run corresponds to a nominal time delay between the X-ray
 pulse and the optical laser pulse. Within each run folder, the images are
 numbered for each X-ray pulse used. The timetool images and the XRD images
 are collected simultaneously. An XRD image corresponds to a unique
 timetool image. For instance "XRD_dataset/r295/XRD_r295_0.tif"
 corresponds to "timetool_dataset/r295/TT_r295_0.tif". We also
 include an image of the focal spot for r256. This run was used to define t
 = 0 ps between the optical laser pulse and the X-ray pulse. More details
 are found in the supplementary information. For the data presented in the
 manuscript, we have filtered the images within each run based on the
 signal on the timetool. When the timetool singal could not been seen we
 discarded this X-ray pulse since we could not obtain a precise timing. The
 timetool signal is stronger for r256 because the thickness of SiN was
 larger than the other runs. ## Description of the logbook sheet * Column
 "Run Number": Number of folder corresponding to the same
 experimental conditions * Column "Change timing based position of
 translation stage of timetool (MEC:LAS:MMN:19.RBV) [mm]" When
 changing the time delay between the optical laser pulse and the X-ray
 pulse, timing on the timetool needs to be compensated by a delay stage.
 The values in this column report the position of the delay stage. * Column
 "Change relative timing based on delay stage compared to run 256
 (reference for defining t = 0ps)" This column converts the position
 of the previous column into a time delay. The reference is taken to be the
 position of r256 which define t = 0 ps. * Column "Laser triggering
 time (LAS:FS6:VIT:FS_TGT_TIME) [ns]" These values correspond to the
 triggering time of the short pulse laser system. * Column "Change
 relative timing on laser triggering compared to r256 Vitara [ps]"
 These values calculate the triggering time from the previous column into a
 time delay using r256 as a reference. * Column "Comments"
 Comments for each run. The numerical values correspond to the targeted
 time delay for each run. Column E corresponds to the actual time delay of
 the run. These values are within 0.1 ps of the targeted time delay. To
 reach the timing accuracy described in the main manuscript we need to use
 the time tool. However, as seen in column C, the time delay on the time
 tool doesn't match the values in column E. If we use the time tool
 with the pixel position found for t = 0 ps using r256 (analysis in
 Materials and Methods), then we would measure a time delay that is offset
 by the value of C-E. This offset needs to be compensated. For run 288,
 only X-ray pulses were present. The optical laser was not fired so no
 values for columns B to E are present. We use "NA" to represent
 this.