Description:
Abstract A broad-band femtosecond spectroscopy apparatus has been developed. The spectrum of the probe light pulse extends from 400 nm to 3.0 μm, covering near ultraviolet (NUV), visible (VIS), and near infrared (NIR) ranges. The time resolution is better than 100 fs in the NUV and VIS regions, and better than 200 fs in the NIR region. The minimum detectable absorbance change is 2 × 10−3 for wavelengths between 400 nm and 1.6 μm and 3 × 10−3 between 1.6 μm and 3.0 μm. A tunable light pulse for the pump was also developed using the second-harmonic generation (SHG) and sum-frequency generation (SFG) in the cavity of the optical parametric oscillator. The tuning ranges of SHG and SFG are 529—585 nm and 426—483 nm, respectively. The study of ultrafast geometrical relaxation processes in a substituted poly(phenylacetylene) by the use of the broad spectroscopy apparatus is described as an example at the end.