Fig. 3. Assignment of molecular species formed in the discharge of benzene to the structures presented in Fig. 4a–m using mass-selective IR spectroscopy (black) with calculated IR absorption spectra (red). The mass channels shown are m/z = (a) 91, (b) 102, (c) 115, (d) 126, (e) 128, (f) 150, (g) 152, (h) 154, (i) 166, (j) 178, (k) 192, (l) 204, (m) 228 and (n) 230. The molecules assigned to each mass are (a) tropyl radical, (b) phenylacetylene, (c) tropylacetylene radical, (d) phenyldiacetylene, (e) naphthalene, (f) phenyltriacetylene, (g) 1- and 2-ethynylnaphthalene (1 : 2), (h) biphenyl, (i) fluorene, (j) diphenylacetylene and phenanthrene (2 : 1), (k) 1- and 2-phenyl-H-indene (2 : 1), (l) 1- and 2-phenylnaphthalene (1 : 1), (m) triphenylene and (n) p-terphenyl. For m/z 152, the blue trace consists for 50% of the FT-IR reference spectra of 1- and 2-ethynylnaphthalene (1 : 2) and for 50% of the experimental spectrum of m/z = 154.