Additionally, it shows a broad and strong positive signature between 5 Å and 7 Å. The differences can, again, be easily explained based on the reactant and product structures. The positive contributions from the R1 and R2 distances at 2.5 Å are overwhelmed in the ∆PDF by negative signatures from the increase of the (isopropyl-carbon, ring-carbon) distances. These distances increase substantially due to the rehybridization of the methylene groups, which rotates the isopropyl substituent into the plane of the conjugated π system. The resulting overall stretching of the molecule results in the positive signatures in the area between 5 Å and 7 Å. The additional signatures from photochemically forbidden reaction products of the two types of conformers in Fig. show that diffraction probing is sufficiently sensitive to even distinguish violations of the Woodward-Hoffmann rules. CHD. The nonadiabatic wavepacket dynamics of each of the six conformer structures in Fig. were simulated separately. Figure shows superpositions of the resulting ∆PDF signatures of the three quasi-equatorial conformers in Fig. &) and the three quasi-axial conformers in Fig. & 6f. The comparison to the experimental signatures confirms the interpretation of the ∆PDFs with carbon-carbon distances marked. Note the alignment of the vertical axes in all panels (a-c). (d) Simulated temporal evolution of the (C3, C4) bond distance of α-terpinene (αTp) in the excited state (S1, blue) and the ground state (S0, black). Additionally, the time-dependent population of S0 is plotted (pink). The atom labeling is shown in the inset. Figure reproduced from Reference (77) (CC BY 4.0).