Applications

Spectral dynamics of beta-carotene in solution acquired using HARPIA-TA. Measurement conditions: 100 kHz repetition rate, 490 nm pump wavelength, < 10 nJ pump pulse energy, 13 s per spectrum (per delay point) acquisition time.

Pump-dump-probe dynamics of DCM laser dye with dump pulse resonant to the emission band of DCM. Measurement conditions: 50 kHz repetition rate, 515 nm pump wavelength, 700 nm dump wavelength, 21 ps dump delay, 90 nJ pump pulse energy, 190 nJ dump pulse energy.

The transient absorption (TA) experiment allows quantitative characterization of time-dependent absorption of an optically excited sample. Two light pulses are required: 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 probe wavelength and the temporal delay between the pump and probe pulses.

The TA 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 both on the ground and the excited states.

In HARPIA-TA, the TA experiment can be easily customized to get additional insight into the ultrafast dynamics of photoactive systems. For example, measuring transient reflection instead of absorption would provide more details on material surface photodynamics. Performing pump intensity-resolved absorption would help estimate the annihilation and saturation processes. Carrying TA experiments with different linear or circular pump pulse polarizations would allow obtaining molecular aggregation properties or molecular-level chirality-dependent spectra.

When the transient spectroscopy is not enough, the HARPIA-TA spectrometer can be expanded to perform time-resolved multi‑pulse and fluorescence spectroscopies using HARPIA-TB and HARPIA-TF modules, respectively.