© Ultrafast Systems LLC /Vernier Software & Technology
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A white light LED is utilized for probing the spectral changes taking place after the sample has
been exposed to an excitation flash. The white light is sent through a sample cuvette via lens L1 and
subsequently delivered to the photodetector diode by passing through an optical interference filter and
objective lens L2. The optical interference filter is used to select the desired wavelength out of the broad
emission spectrum of the LED. While the continuous wave (CW) output from the LED is being monitored
by the photodiode, the photoexcitation flash is sent through the sample. The photo-induced transient
species cause the absorption of the sample to deviate from what it was before the excitation flash. This
results in changes in the intensity of the LED light passing through the sample. These changes are
detected by the monitoring photodiode. The output voltage waveform from the photodiode is collected
and digitized by an internal DAQ device and transferred to the computer for further manipulation.
