Picosecond time-resolved infrared absorption study on the electron-molecular vibration interactions of the dimers in the electronically excited states

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1.Construction of a picosecond time-resolved infrared absorption spectrometer with time resolution of 【approximately equal】 3 ps and spectral resolution of 【approximately equal】 4 cm^<-1>.The fundamental output (wavelength 775 nm, pulse width 【approximately equal】 2.1 ps, repetition rate 1 kHz) from a picosecond Ti : sapphire regenerative amplifier seeded by the second harmonic of a mode-locked Er-doped fiber laser (Clark-MXR CPA-2000) was used to excite an optical parametric generator and amplifier (Quantronix TOPAS). Widely tunable picosecond light pulses in the 2500 nm - 11 μm (4000 - 900 cm^<-1>) range were obtained by difference-frequency generation in an AgGaS_2 crystal between the signal and idler waves from the optical parametric generator and amplifier. The wavenumber bandwidth of the tunable infrared light pulses was 【approximately equal】 16 cm^<-1>. We achieved the spectral resolution of 【approximately equal】 4 cm^<-1> by using a dispersive spectrometer.2.Syntheses of some d … More imer molecules and measurements of picosecond time-resolved infrared absorption spectra of their excited states.We synthesized some dimer molecules and measured the picosecond time-resolved infrared absorption spectra of them in the electronically excited states. Optimizations of molecular structures and vibrational analyses for the excited states of dimer molecules were performed based on molecular orbital calculations. The electron-molecular vibration interactions will be discussed.3.Infrared absorption measurements of π-conjugated radical anions and dianions in solution and spectral analyses based on density functional theory calculations.High-quality infrared spectra were observed for the radical anions and dianions of naphthalene, anthracene, biphenyl, and p-phenyl in tetrahydrofuran solutions. Observed infrared spectra were in good agreement with those calculated by density functional theory. The origin of the strong infrared absorption intensities characteristic of the radical anions and dianions were discussed in terms of changes in electronic structures induced by specific normal vibrations (electron-molecular vibration interaction). Less