Lecture

Photochemistry Fundamentals

Graph Chat

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

In course

CH-442: Photochemistry

This course presents the theoretical bases of electronic spectroscopy and molecular photophysics. The principles of the reactivity of excited states of molecules and solids under irradiation are detailled. The main classes of industrial and natural photoc ...

Description

This lecture covers the fundamental concepts of photochemistry, including the kinetics of excited state's radiative decay, Jablonski's diagram, spin correlation effect, non-radiative and radiative deactivation processes, Stokes shift, emission spectrum, solvation dynamics, and kinetic competition of deactivation processes. It also discusses the selection rules for non-radiative processes, spin-orbit coupling, and quenching of the emission, providing insights into the intricate processes governing photochemical reactions.

Official source

Related concepts (32)

Photochemistry

Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible light (400–750 nm) or infrared radiation (750–2500 nm). In nature, photochemistry is of immense importance as it is the basis of photosynthesis, vision, and the formation of vitamin D with sunlight. It is also responsible for the appearance of DNA mutations leading to skin cancers.

Jablonski diagram

In molecular spectroscopy, a Jablonski diagram is a diagram that illustrates the electronic states and often the vibrational levels of a molecule, and also the transitions between them. The states are arranged vertically by energy and grouped horizontally by spin multiplicity. Nonradiative transitions are indicated by squiggly arrows and radiative transitions by straight arrows. The vibrational ground states of each electronic state are indicated with thick lines, the higher vibrational states with thinner lines.

Fluorescence

Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation. A perceptible example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the electromagnetic spectrum (invisible to the human eye), while the emitted light is in the visible region; this gives the fluorescent substance a distinct color that can only be seen when the substance has been exposed to UV light.

Emission spectrum

The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an electron making a transition from a high energy state to a lower energy state. The photon energy of the emitted photon is equal to the energy difference between the two states. There are many possible electron transitions for each atom, and each transition has a specific energy difference. This collection of different transitions, leading to different radiated wavelengths, make up an emission spectrum.

Fluorescence spectroscopy

Fluorescence spectroscopy (also known as fluorimetry or spectrofluorometry) is a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electrons in molecules of certain compounds and causes them to emit light; typically, but not necessarily, visible light. A complementary technique is absorption spectroscopy. In the special case of single molecule fluorescence spectroscopy, intensity fluctuations from the emitted light are measured from either single fluorophores, or pairs of fluorophores.

Related lectures (34)

Fluorescence in Microscopy: Introduction & Labeling Techniques

Covers the introduction to fluorescence in microscopy, labeling techniques, specificity of markers, multi-color imaging, and factors affecting fluorescence properties.

Fluorescence Spectroscopy: Principles and Applications

Explores fluorescence spectroscopy principles, applications in photomedicine, and biological fluorophores.

Organic Light Emitting Diodes (OLEDs)

Covers the fundamentals of OLEDs, including basic operation, exciton dynamics, charge transport, and emission pathways.

Applications of Optical Spectroscopy in Photomedicine

Explores optical spectroscopy in photomedicine, emphasizing fluorescence principles, biological fluorophores, and fluorescence lifetime measurements.

Photochemistry: Excited State Dynamics