were obtained by streak-camera measurements. A frequency doubled Ti-Saphire
Laser (Tsunami, Newport Spectra-Physics GmbH) was used as the light
source to generate the 390 nm excitation pulses. The pulse-to-pulse
repetition rate of the laser was reduced to 4 kHz by a pulse selector
(Model 3980, Newport Spectra-Physics GmbH). The emission was recorded
using a CHROMEX 250IS spectrograph and a Hamamatsu HPD-TA streak-camera.
The power of the pump-pulse used was in the range of 0.2 mW, and the
OD of the sample at the excitation wavelength was in the range of
0.05 to 0.1.