Newton diagram illustrating the kinematic constraints for the photodissociation channels of vinylacetylene (C₄H₄) at 193 nm. The primary beam velocity vector is shown along the vertical axis, while the concentric circles represent the maximum scattering angle of product fragments for different dissociation channels. The inner three circles correspond to H loss channels (m/z = 51), whereas the intermediate two circles represent H₂ loss channels (m/z = 50). The outer circles correspond to C₂H₂/CCH₂ loss channels (m/z = 26), including symmetric and asymmetric fragmentations such as HC≡CH + HC≡CH, HC≡CH + C=CH₂, and C=CH₂ + C=CH₂.