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Raman spectra of the mono-negative ion of biphenyl in tetrahydrofuran solution were obtained by Ar+, He–Ne and Kr+ laser exciting lines. The observed frequency shift from the neutral molecule and intensity enhancement by resonance Raman effect is discussed on the basis of MO considerations.

13C NMR spectra of undoped polyacetylene,(CH)x, have been measured. The existence of 3.4 mol% methylene moieties as defects in the (CH)x chains has been observed in trans-(CH)x. Measurements of partially cis-to-trans isomerized (CH)x suggest the existence of isolated cis regions.

The resonance Raman effect of I 2 was observed in chloroform, benzene- d 6 and tetrahydrofuran solutions with eleven exciting frequencies by Ar + , Kr + and He-Ne lasers. Excitation profiles obtained for the ν I-I fundamental in benzene- d 6 and tetrahydrofuran showed apparently different features from that of chloroform. It is demonstrated in a simulative calculation that the anomalous profile in the former two solvents could be caused by the interference between partial contributions to the scattering tensor, one from the locally excited state responsible for the visible absorption and the other from the charge-transfer state, both of the complex formed.

Two-photon absorption spectra of trans- and cis-1,3,5-hexatrienes in the liquid state have been observed in the frequency range of 2ω = 30000–50000 cm−1, by analyzing the interference effect of Raman and two-photon resonances in the CARS and CSRS lineshape. In both isomers, a broad two-photon absorption with a maximum absorptivity of about 10−50 cm4 s photon−1 molecule−1 was determined to be a few thousand cm−1 higher than an intense dipole-allowed transitions (11Bu ← 11Ag or 11B2 ← 11A1) near 40000 cm−1. This band is most probably assigned to the two-photon-allowed state corresponding to the lowest excited singlet already established to be 21Ag or 21A1 in larger homologues. The relative ordering of the 11B and 21A levels is discussed.

Raman spectra of anthracene mono- and di-negative ions in tetrahydrofuran solution were obtained by HeNe and Ar + laser exciting lines. In addition to some frequency shifts from neutral anthracene, remarkable enhancement of intensities by the resonance Raman effect was observed for many aromatic ring vibrations.

Resonance Raman spectra have been observed for the dimers of p -phenylenediamine cation (PPD + ) and of 2,3,5,6-tetramethyl- p -phenylenediamine cation (TMPD + ). When the exciting light frequency approached the absorption bands characteristic of the dimers, new polarized Raman lines appeared at 161 cm −1 for (PPD + ) 2 and at 117 cm −1 for (TMPD + ) 2 with a striking resonance enhancement. The resonant behaviour as well as the frequency values indicate that they are reasonably assigned to the interradical stretching vibrations of the parallel D 2h dimer molecules.

Raman spectra of VCl 4 and SnI 4 in solution are obtained using the exciting lines of a HeNe and an Ar + laser. The spectra show a pre-resonance Raman effect with an enhancement of the stretching vibrations for shorter wavelengths of excitation. The features of the intensity variation are discussed quantitatively in terms of the frequency factors given by Albrecht and Hutley.