Fotofysica

Fotofysica, or photophysics, is the branch of physics that studies the physical processes that occur when light interacts with matter. It focuses on how optical excitation leads to electronic, vibrational, and spin transitions, and on how excited states relax back to equilibrium through radiative and non-radiative pathways. The field covers gases, liquids, and solids, including organic molecules, dyes, semiconductors, and nanoscale materials.

Key concepts in fotofysica include absorption of photons, radiative processes such as fluorescence and phosphorescence, and non-radiative decay through vibrational relaxation or coupling to vibrations and phonons. Excited-state dynamics often involve energy transfer between molecules (Förster and Dexter mechanisms), intersystem crossing between singlet and triplet states, and the formation and diffusion of excitons in solids. Quantities such as quantum yield, excited-state lifetime, absorption and emission cross sections, and rate constants help quantify these processes. The Jablonski diagram is a common schematic tool used to represent electronic states and transitions.

Methods and theory in fotofysica span spectroscopy, time-resolved measurements, and quantum-chemical calculations. Experimental techniques include absorption, steady-state and time-resolved fluorescence, phosphorescence spectroscopy, transient absorption, and photoacoustic methods. Theoretical frameworks rely on quantum mechanics, rate equations, and models of energy transfer and relaxation.

Applications of fotofysica are broad and include light-emitting devices, solar cells, photocatalysis, imaging and sensing, and the development of materials with tailored optical properties. The field underpins advances in both fundamental science and technology.