Transient Absorption Microscopy
The transient absorption (TA) experiment allows for the quantitative characterization of time-dependent absorption of an optically excited sample. This technique requires two light pulses: a femtosecond narrow-bandwidth pump pulse to excite the sample and delayed broad-bandwidth probe pulse to measure the changes in sample transmittance. The resulting difference absorption signal is measured as a function of the probe wavelength and the temporal delay between the pump and probe pulses.
The transient absorption spectrum is much more elaborate than, e.g., a steady-state absorption or fluorescence decay spectrum. It provides information not only on the excited states of the system but also on all the intermediate evolutionary transients and non-emissive states in both the ground and excited states.
HARPIA-TA can be equipped with a microscopy module HARPIA-MM, enabling spatially-resolved pump-probe measurements with a spatial resolution down to 5 μm. The HARPIA-MM module features a brightfield mode to observe the sample and determine the pump-probe spot location and transmission and reflection modes to carry out the pump-probe measurements.
Pump-probe kinetics of a single perovskite crystallite. The pump-probe spot is marked by a small circle.
Measurement conditions: 200 kHz repetition rate, 400 nm pump wavelength, 2 nJ pump pulse energy, 0.5 s per spectrum acquisition time, and Plan Fluor 4x/0.13 objective.
