We present comprehensive experimental line lists of methane (CH 4 ) at high temperatures obtained by recording Fourier transform infrared emission spectra. Calibrated line lists are presented for the temperatures 300 -1400 • C at twelve 100 • C intervals spanning the 960 -5000 cm −1 (2.0 -10.4 µm) region of the infrared. This range encompasses the dyad, pentad and octad regions, i.e., all fundamental vibrational modes along with a number of combination, overtone and hot bands. Using our CH 4 spectra, we have estimated empirical lower state energies (E low in cm −1 ) and our values have been incorporated into the line lists along with line positions (ν in cm −1 ) and calibrated line intensities (S ′ in cm molecule −1 ). We expect our hot CH 4 line lists to find direct application in the modeling of planetary atmospheres and brown dwarfs.

A series of oligothienylenevinylenes, pi-conjugated oligomers rigidified by ethylene bridges attached at different sites of the conjugated backbone, have been constructed by multistep synthetic methodologies. Electronic absorption spectra show that the rigidification of the conjugated system produces a bathochromic shift of the absorption maximum and a narrowing of the HOMO-LUMO energy gap, as compared to the spectra of an open-chain reference compound. The cyclic voltammograms of all oligomers show that these compounds can be reversibly oxidized into their cation radicals and dications and that rigidification produces a large negative shift of the first oxidation potential, which is indicative of a considerable increase of the HOMO level. Electrochemical data confirm that covalent bridging strongly affects the HOMO and LUMO levels and these data demonstrate that the sites of fixation of the bridges on the pi-conjugated backbone exert a determining effect on the relative stability of the cation radical and dication. Examination of these various results in the light of theoretical calculations shows that in addition to a local control of bond length alternation, and hence of the HOMO-LUMO gap, the fixation of covalent bridges at selected positions of the pi-conjugated system limits the deformation of the pi-conjugated structure upon oxidation to the charged states.

Replacement of the open chain dithienylethylene p-conjugating spacer by its bridged analog in push-pull NLOphores produces a dramatic increase of the quadratic hyperpolarisability.