This data set contains all data underlying the figures in the main text and supporting information. The information on how the data was acquired and processed is detailed in the open access manuscript + SI which has been deposited in this repository and is also available open-access via the publisher Nature Communications under the title "Direct Observation of Ultrafast Singlet Exciton Fission in Three Dimensions". All the extracted data can also be generated from the experimental data by running the model described in the Main text.

Main Figures: Fig 1 - b) Transient transmission and complex refractive index slices of pentacene, c) z-stack dependent transient transmission images of pentacene on two spectral bands radially averaged, d) image of the sample of pentacene on hBN. Fig 2,3 and 4 - Underlying datasets of transient transmission images (DTT) on glass and on hBN are provided in two folders 'onGlass' and 'onhBN'. In each the DTTs.npy file is meant to be opened using the python numpy library and the numpy.load command, yielding a 3 dimensional array, where the first axis is time and the second and third axis index X and Y position. The time.txt file give the pump probe delay corresponding to the first axis index. Each pixel (X and Y) corresponds to 55.5 nm in real space. The glass dataset is radially averaged to provide Fig 2/3/4 a and the radial slices in Fig 2/3/4 b (the full images are plotted above it). Upon fitting the radial averaged to the model described in the main text with appropriate bounds yields Fig 2/3/4 d-g.