C2H2 : polyatomic molecule

acetylene

C

C

C

H

C

H

vinylidene

H

H

1 T. Osipov, C. L. Cocke, M. H. Prior, A. Landers, Th. Weber, O. Jagutzki, L. Schmidt, H. Schmidt-Böcking, and R. Dörner, Phys. Rev. Lett. 90, 233002 (2003).