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Questions and Answers
What is the definition of phosphorescence?
What is the definition of phosphorescence?
- Emission of light by internal conversion of triplet excited state molecules
- Delayed and long-lived emission of light by triplet excited state molecules (correct)
- Immediate emission of light by singlet excited state molecules
- Emission of light by collision of excited singlet state molecules
What are some natural phosphors mentioned in the text?
What are some natural phosphors mentioned in the text?
- Zinc oxide (ZnO)
- Zinc sulfide (ZnS) (correct)
- Barium titanate (BaTiO3)
- Strontium titanate (SrTiO3)
Why do phosphorescent materials store and re-emit light?
Why do phosphorescent materials store and re-emit light?
- As a result of rapid de-excitation from triplet state to singlet state
- Because of their unusual property of trapping their electrons in a higher energy state (correct)
- Due to their ability to trap photons for a long time
- Because of their ability to convert UV light into visible light
What happens once a molecule is in the triplet state?
What happens once a molecule is in the triplet state?
What is the process involved in the deactivation from an excited "triplet" electronic state to the ground "singlet" electronic state producing a photon?
What is the process involved in the deactivation from an excited "triplet" electronic state to the ground "singlet" electronic state producing a photon?
What is the definition of phosphorescence?
What is the definition of phosphorescence?
What is the process involved in the deactivation from an excited 'triplet' electronic state to the ground 'singlet' electronic state producing a photon?
What is the process involved in the deactivation from an excited 'triplet' electronic state to the ground 'singlet' electronic state producing a photon?
Why do phosphorescent materials store and re-emit light?
Why do phosphorescent materials store and re-emit light?
Which minerals are mentioned as natural phosphors in the text?
Which minerals are mentioned as natural phosphors in the text?
What occurs once a molecule is in the triplet state?
What occurs once a molecule is in the triplet state?
What is the definition of phosphorescence?
What is the definition of phosphorescence?
Which minerals are mentioned as natural phosphors in the text?
Which minerals are mentioned as natural phosphors in the text?
What occurs once a molecule is in the triplet state?
What occurs once a molecule is in the triplet state?
Why do certain minerals glow in the dark when exposed to UV light?
Why do certain minerals glow in the dark when exposed to UV light?
What is the process involved in the deactivation from an excited 'triplet' electronic state to the ground 'singlet' electronic state producing a photon?
What is the process involved in the deactivation from an excited 'triplet' electronic state to the ground 'singlet' electronic state producing a photon?
Study Notes
- Phosphorescence is the delayed and long-lived emission of light by triplet excited state molecules following absorption of photons from an external source.
- Certain minerals, such as Zinc sulfide (ZnS) and Strontium aluminate (SrAl2O4), are natural phosphors that emit light in the dark after being exposed to UV light.
- Phosphorescent materials store and re-emit light due to their ability to trap electrons in a higher energy state for minutes or even hours.
- After absorbing a photon, an electron in a molecule can transition from a singlet to a triplet electronic state through a process called intersystem crossing.
- In the triplet state, de-excitation to the ground singlet state is forbidden due to a change in electron spin, causing the molecule to hang in the triplet state and release energy slowly, resulting in phosphorescence.
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Description
Learn about the delayed and long-lived emission of light by triplet excited state molecules following absorption of photons from an external source, known as phosphorescence. Discover how certain minerals glow in the dark and continue to emit light even after the UV light is turned off.
