timeresolved

Timeresolved refers to a set of experimental approaches that determine how a physical, chemical, or biological system evolves in time following an initiated event. In a typical timeresolved experiment, a short excitation pulse (the pump) triggers dynamics, and a second controlled pulse or a detector measures the evolving signal at various delays (the probe). The resulting time-dependent signal reveals reaction pathways, energy transfer, conformational changes, or charge and spin dynamics. Temporal resolution is governed by the instrument response function and the duration of the light pulses, often ranging from femtoseconds to nanoseconds.

Common timeresolved techniques include time-resolved spectroscopy, such as transient absorption and time-resolved fluorescence; time-resolved microscopy and imaging; and time-resolved mass spectrometry. Sophisticated implementations employ streak cameras, time-correlated single-photon counting, or ultrafast X-ray sources for higher time resolution. Experimental setups typically require ultrafast lasers, optical delay lines, synchronized detectors, and careful control of sample conditions.

Data from timeresolved experiments are analyzed by fitting kinetic models to decay traces, performing global and target analysis to extract species-associated spectra, and convolving models with the instrument response. The field is associated with femtochemistry, pioneered by Ahmed Zewail, and has expanded into chemistry, materials science, biology, and energy research.

Applications include studying photoinduced reactions, charge transfer in photovoltaics, protein dynamics, and phase transitions in materials. Ongoing trends include single-molecule timeresolved measurements and timeresolved X-ray and electron microscopy, enabling access to faster processes and heterogeneity.