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Where UV-vis spectroscopy becomes useful to most organic and biological chemists is in the study of molecules with conjugated \(\pi\) systems. In these groups, the energy gap for π - π * transitions is smaller than for isolated double bonds, and thus the wavelength absorbed is longer.
16 Μαρ 2023 · To consider what happens in the process of fluorescence, we need to think of the possible energy states for a ground and excited state system. Draw an energy level diagram for a typical organic compound with \(\pi\) and \(\pi\) * orbitals.
In quantum mechanics, an excited state of a system (such as an atom, molecule or nucleus) is any quantum state of the system that has a higher energy than the ground state (that is, more energy than the absolute minimum).
29 Μαΐ 2024 · An excited state refers to a condition of an atom or molecule in which its energy is higher than the ground state. The ground state is the lowest energy state of the atom. When an atom absorbs energy, its electrons jump from a lower energy level to a higher one, resulting in an excited state.
A Jablonski diagram showing the excitation of molecule A to its singlet excited state (1 A*) followed by intersystem crossing to the triplet state (3 A) that relaxes to the ground state by phosphorescence. It was used to describe absorption and emission of light by fluorescents.
Use linear response theory on top of DFT to find the excitation energies. This leads to the Casida equations, which can be a little complicated to solve. We can simplify the Casida equations using the “Tamm-Dancoff” approximation (TDA), which yields results that are just as good.
Fluorescence is a member of the ubiquitous luminescence family of processes in which susceptible molecules emit light from electronically excited states created by either a physical (for example, absorption of light), mechanical (friction), or chemical mechanism.
