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The excited, triplet state photosensitizer then reacts with a substrate molecule which is not molecular oxygen to both form a product and reform the photosensitizer. Type I photosensitized reactions result in the photosensitizer being quenched by a different chemical substrate than molecular oxygen.
Non-photochemical quenching (NPQ) is a mechanism employed by plants and algae to protect themselves from the adverse effects of high light intensity.It involves the quenching of singlet excited state chlorophylls (Chl) via enhanced internal conversion to the ground state (non-radiative decay), thus harmlessly dissipating excess excitation energy as heat through molecular vibrations.
Examples of atoms in singlet, doublet, and triplet states. In quantum mechanics, a triplet state, or spin triplet, is the quantum state of an object such as an electron, atom, or molecule, having a quantum spin S = 1. It has three allowed values of the spin's projection along a given axis m S = −1, 0, or +1, giving the name "triplet".
The spin relationship is such that the two unpaired electrons, one in each radical molecule, may have opposite spin (singlet; anticorrelated), or the same spin (triplet; correlated). The singlet state is called such because there is only one way for the electrons’ spins to anticorrelate (S), whereas the triplet state is called such because ...
In the ground state of dioxygen, this energy level is occupied by two electrons of the same spin, as shown in the molecular orbital diagram. The molecule, therefore, has two unpaired electrons and is in a triplet state. In contrast, the first and second excited states of dioxygen are both states of singlet oxygen. Each has two electrons of ...
Upon absorption of light, carotenoids transfer excitation energy to and from chlorophyll. The singlet-singlet energy transfer is a lower energy state transfer and is used during photosynthesis. [7] The triplet-triplet transfer is a higher energy state and is essential in photoprotection. [7]
Examples of atoms in singlet, doublet, and triplet states.. In quantum mechanics, a doublet is a composite quantum state of a system with an effective spin of 1/2, such that there are two allowed values of the spin component, −1/2 and +1/2.
In a triplet state the excited electron is no longer paired with the ground state electron; that is, they are parallel (same spin). Since excitation to a triplet state involves an additional "forbidden" spin transition, it is less probable that a triplet state will form when the molecule absorbs radiation. Singlet and triplet energy levels.