| singlet oxygen | An energised but uncharged form of oxygen that is produced in the metabolic burst of leucocytes and that can be toxic to cells. (18 Nov 1997) |
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| singlet state | A transient, excited state of a molecule (e.g., of chlorophyll, upon absorbing light) that can release energy as heat or light (fluorescence) and thus return to the initial (ground) state; it may alternatively assume a slightly more stable, but still excited state (triplet state), with an electron still dislocated as before but with reversed spin. (05 Mar 2000) |