Editing Time-resolved spectroscopy (section)

===Application===
Transient absorption spectroscopy helps study the mechanistic and kinetic details of chemical processes occurring on the time scales of a few picoseconds to femtoseconds. These chemical events are initiated by an ultrafast laser pulse and are further probed by a probe pulse. With the help of TA measurements, one can look into non-radiative relaxation of higher electronic states (~femtoseconds), vibrational relaxations (~picoseconds), and radiative relaxation of excited singlet state (occurs typically on a nanoseconds time scale).

Transient absorption spectroscopy can be used to trace the intermediate states in a photochemical reaction; energy, charge, or electron transfer process; conformational changes, thermal relaxation, fluorescence or phosphorescence processes, [[semiconductor optical gain|optical gain]] spectroscopy of semiconductor laser materials, etc. With the availability of UV-Vis-NIR ultrafast lasers, one can selectively excite a portion of any large molecule to desired excited states to study the specific molecular dynamics, such as photo-protective functions of carotenoids in photosynthesis.<ref>https://link.springer.com/article/10.1007/s11120-009-9454-y#Abs1</ref>

Transient absorption spectroscopy has become an important tool for characterizing various electronic states and energy transfer processes in nanoparticles, to locate trap states, and further helps in characterizing the efficient passivation strategies.<ref>C. Burda and M. A. El-Sayed, Pure Appl. Chem., 2000, Vol. 72, No. 1-2, pp. 165-17.</ref>