Femtosecond transient absorption spectra were measured by a UV pump-supercontinuum probe technique using a homebuilt spectrometer based on an amplified Ti:Sa laser system, described in detail in our previous communication. Part of the 800 nm Ti:Sa beam (1 mJ, 50 fs, 1 kHz repetition rate) was frequency was doubled in a β-barium borate (BBO) crystal, chopped at 500 Hz, and used as the pump. A portion of the 800 beam was delayed with a linear translation stage and used for supercontinuum generation in a sapphire crystal. The supercontinuum probe beam, spanning the 430-750 nm wavelength range, was further split into and signal and reference beams that were spectrally dispersed and registered shot-to-shot with two CCD sensors. The instrument response function was less than 100 fs (fwhm) over the entire spectrum. The data were averaged over 5-9 scans to improve the signal-to-noise ratio. Measurement control was realized by in-house written software. Routines for data pre-processing (coherent artifact and GVD correction) and analysis were developed in our laboratory. For the TOAS measurements samples with an absorbance around 0.5 at the absorption maximum were used.