Metadata of measurement_2.h5 

Experimental method: time-resolved electron diffraction experiment on pentacene single crystals  
Location of the experiment: Fritz Haber Institute, Faradayweg 4-6, 14195 Berlin, Department of Physical Chemistry, Research Group Structural and Electronic Surface Dynamics  
Date of the experiment: March 3rd, 2020 
Related publication / description of the experiment: https://arxiv.org/abs/2011.12016

Sample parameters  

material: pentacene single crystals 
sample provider: Sebastian Hammer from the group of Prof. Dr. Jens Pflaum in Julius-Maximilians-University Würzburg, Experimental Physics VI
sample thickness: (50 +/-5) [nm] 
absorbed photons per unit volume: around 10^20 [1/cm^3]
sample temperature: 300  [K] 


Optical pump pulse parameters  

pump pulse repetition rate: 4 [kHz] 
pump pulse duration: ca. 50 [fs]  
pump pulse center wavelength: 680 [nm]  
pump pulse spot size at sample: ca. 150 [um] 
pump pulse incident fluence:  0.4 [mJ/cm^2] 
pump pulse polarization: linear, parallel to a-axis of the crystal 
pump pulse angle of incidence: 10° off-normal  


Electron probe pulse parameters 
 
electron probe pulse repetition rate: 4 kHz 
electron energy: 70 [keV]  
electron spot size at sample: ca. 100 [um]  
electron probe pulse angle of incidence: normal  
diffraction geometry: in transmission  


Estimated time resolution of the experiment: ca. 250 fs 


Electron detector parameters: 
 
detector manufacturer: TVIPS GmbH, Germany 
detector model: TemCam F-416 
detector pixel size: 15.6 x 15.6 [um^2]  
detector binning: none 
integration time: 10 [s] 


Pump-probe scan parameters: 

126 discrete pump-probe delays are sampled between -2 ps and +8 ps (dataset "delays [ps]" in group "Measurement").
The pump-probe range is scanned 47 times in alternating direction.
At each delay point, the diffraction signal is measured for 30 s (3 burst acquisitions a 10 s), 
resulting in 5922 images. 

In addition, a background image (no electron probe pulse; with optical pump pulse) was recorded 
with the same acquisition parameters. This image contains the dark counts and optical pump laser 
light background. 

The raw diffraction images were processed in the following way:  

- The background image was subtracted. 
- The images were flat-field corrected to account for slightly different sensitivities of different pixels of the electron detector.  

Following these operations, an average image over all 47 scans is then obtained for each delay point, yielding 126 images.
These are given in the group "Measurement" in "images". In addition to the operations mentioned above, the following operations were performed on the averaged data:

- Each image was normalized by the average electron flux at the corresponding delay (after each image, an additional low-exposure (100 ms) reference image was acquired. In this reference image, counts were integrated in the non-saturated zeroth order beam. The counts in the zeroth order were then used to normalize the image.). 
- Each dead pixel was assigned a "nan" value. 
- Each image (2048 x 2048 pixels) was cropped to a region of interest (640 x 640) centered on the diffraction pattern so as to save space.

The group "analysis" contains relative intensities of diffraction peaks (e.g. (020)) over the -2 ps to 7.7 ps range. These were extracted using the fitting procedure described in https://arxiv.org/abs/2011.12016.
The corresponding delay points are given in "analysis" under "delays". A running average with a four-point window was applied to highlight the oscillations.