Reactants C4H and HC4H were synthesized from 1% C2H2/He in two crossed molecular beams by pulsed high-voltage discharge. We measured the angle-specific time-of-flight spectra and the photoionization-efficiency spectrum of product C8H2 using a crossed-molecular-beam quadrupole-mass apparatus and synchrotron vacuum-ultraviolet photoionization. The C8H2 product has translational energy stretching to the energetic limit of producing HC8H + H and has an ionization threshold 9.0 +/- 0.1 eV in good agreement with that of HC8H. The quantum-chemical calculations are in accord with the experimental results. This work demonstrates that octatetrayne can be synthesized from the reaction C4H + HC4H -> HC8H + H. (C) 2017 Elsevier B.V. All rights reserved.