Femtosecond Time-resolved Absorption Spectroscopy Research Articles

Polysilane excited states and excited state dynamics

Femtosecond time-resolved excited state absorption spectroscopy is used to reveal excited states of linear-chain poly(di- n-hexylsilane) about 1 eV and in the range of 3.5 eV above the lowest excited state. A description of the excited state dynamics following optical excitation in polysilanes is presented. The concept of conjugation length is discussed in relation to experiments on the saturation of excited state absorption signals observed at high excitation density.

Relaxation dynamics of photoexcitations in polydiacetylene films

The relaxation dynamics of photoexcitations in a polydiacetylene (poly-3BCMU) film was investigated by femtosecond time-resolved absorption spectroscopy. Spectral change due to several nonlinear optical processes, i.e. hole burning, Raman gain, and dynamic Stark effect, was observed. The difference absorption spectra of singlet and triplet excitons minus ground state were measured. The photoexcited singlet excitons relaxed to the self-trapped state with the time constant of 150+or-50 fs. The lifetime of the self-trapped excitons was 2.0+or-0.1 ps at 10 K and 1.5+or-0.2 ps at 290 K. The lifetime of the triplet excitons was much longer than several tens of picoseconds and was consistent with the lifetime of 18 mu s obtained by nanosecond spectroscopy.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>