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Questions and Answers
What happens when a molecule absorbs UV-vis light?
What happens when a molecule absorbs UV-vis light?
- The molecule becomes pyramidal in both S1 and T1 excited states.
- The molecule emits a photon.
- An electron is promoted to a higher energy molecular orbital. (correct)
- The molecule undergoes internal conversion.
What determines the type of electronic transition in a molecule?
What determines the type of electronic transition in a molecule?
- The molecule's color.
- The molecule's density.
- The molecule's size.
- The molecule's functional groups. (correct)
What is the lowest energy electronic transition of formaldehyde?
What is the lowest energy electronic transition of formaldehyde?
- From sigma to sigma*
- From n to sigma*
- From n to pi* (correct)
- From pi to pi*
What is the purpose of infrared and microwave radiation in spectroscopy?
What is the purpose of infrared and microwave radiation in spectroscopy?
What are the two types of relaxation processes from an excited state?
What are the two types of relaxation processes from an excited state?
What is the difference between fluorescence and phosphorescence?
What is the difference between fluorescence and phosphorescence?
What is the molecular orbital diagram for formaldehyde?
What is the molecular orbital diagram for formaldehyde?
What are the factors that affect the relative rates of relaxation?
What are the factors that affect the relative rates of relaxation?
What is the purpose of vibrational and rotational states in spectroscopy?
What is the purpose of vibrational and rotational states in spectroscopy?
What is the difference between fluorescence and phosphorescence lifetimes?
What is the difference between fluorescence and phosphorescence lifetimes?
What is the purpose of internal conversion in spectroscopy?
What is the purpose of internal conversion in spectroscopy?
What happens to formaldehyde in its excited states?
What happens to formaldehyde in its excited states?
What happens when a molecule absorbs UV-vis light?
What happens when a molecule absorbs UV-vis light?
What determines the type of electronic transition in a molecule?
What determines the type of electronic transition in a molecule?
What is the lowest energy electronic transition of formaldehyde?
What is the lowest energy electronic transition of formaldehyde?
What is the purpose of infrared and microwave radiation in spectroscopy?
What is the purpose of infrared and microwave radiation in spectroscopy?
What are the two types of relaxation processes from an excited state?
What are the two types of relaxation processes from an excited state?
What is the difference between fluorescence and phosphorescence?
What is the difference between fluorescence and phosphorescence?
What is the molecular orbital diagram for formaldehyde?
What is the molecular orbital diagram for formaldehyde?
What are the factors that affect the relative rates of relaxation?
What are the factors that affect the relative rates of relaxation?
What is the purpose of vibrational and rotational states in spectroscopy?
What is the purpose of vibrational and rotational states in spectroscopy?
What is the difference between fluorescence and phosphorescence lifetimes?
What is the difference between fluorescence and phosphorescence lifetimes?
What is the purpose of internal conversion in spectroscopy?
What is the purpose of internal conversion in spectroscopy?
What happens to formaldehyde in its excited states?
What happens to formaldehyde in its excited states?
What happens when a molecule absorbs UV-vis light?
What happens when a molecule absorbs UV-vis light?
What determines the type of electronic transition a molecule undergoes?
What determines the type of electronic transition a molecule undergoes?
What happens to formaldehyde's shape when it is in the S1 and T1 excited states?
What happens to formaldehyde's shape when it is in the S1 and T1 excited states?
How many occupied orbitals does the molecular orbital (MO) diagram for formaldehyde show?
How many occupied orbitals does the molecular orbital (MO) diagram for formaldehyde show?
What is the lowest energy electronic transition of formaldehyde?
What is the lowest energy electronic transition of formaldehyde?
What types of motion can infrared and microwave radiation change in a molecule?
What types of motion can infrared and microwave radiation change in a molecule?
What are associated with each electronic state of a molecule?
What are associated with each electronic state of a molecule?
What are the types of relaxation processes from an excited state?
What are the types of relaxation processes from an excited state?
What happens to a molecule after it absorbs light?
What happens to a molecule after it absorbs light?
What does internal conversion convert light into?
What does internal conversion convert light into?
What determines the relative rates of relaxation from an excited state?
What determines the relative rates of relaxation from an excited state?
What is the difference between fluorescence and phosphorescence in terms of lifetime?
What is the difference between fluorescence and phosphorescence in terms of lifetime?
Study Notes
Fundamentals of Spectroscopy: What Happens When a Molecule Absorbs Light?
- Absorption of UV-vis light promotes an electron to a higher energy molecular orbital.
- Different types of electronic transitions require different functional groups.
- Formaldehyde in its ground state is planar, but becomes pyramidal in both S1 and T1 excited states.
- The molecular orbital (MO) diagram for formaldehyde shows four occupied orbitals, including a nonbonding orbital (n) and a pi antibonding orbital (Ï€*).
- The lowest energy electronic transition of formaldehyde is from n to pi*.
- Infrared and microwave radiation can change vibrational, translational, and rotational motion of a molecule.
- Vibrational and rotational states are associated with each electronic state, and transitions between different states can occur.
- Relaxation processes from excited state include vibrational and rotational relaxation through collision with solvent or other molecules, and electronic relaxation through the release of a photon.
- After absorption, a molecule can undergo internal conversion, intersystem crossing, fluorescence, or phosphorescence.
- Internal conversion converts light into heat, while fluorescence and phosphorescence involve emission of a photon.
- The relative rates of relaxation depend on the molecule, solvent, temperature, and pressure.
- Fluorescence has a short lifetime (10-8 to 10-4 s), while phosphorescence has a longer lifetime (10-4 to 102 s).
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Description
Test your knowledge on the fundamentals of spectroscopy and learn what happens when a molecule absorbs light. This quiz delves into the different types of electronic transitions, vibrational and rotational motion, and relaxation processes from excited states. Discover the various ways a molecule can emit light, and the factors that affect the rates of relaxation. If you're fascinated by the science of light and molecules, this quiz is for you.
