Worksheet: Selection Rules in Electronic Transitions

In this worksheet, we will practice using term symbols and selection rules to predict favored electronic transitions in atoms and molecules.

Q1:

In symmetry terms, which of the following must be true for an allowed transition?

  • AOnly the vibrational representations must be symmetric.
  • BOnly the electronic representations must be symmetric.
  • CSymmetry does not matter, as long as there is a change in dipole or polarizability.
  • DBoth the electronic and vibrational representations must be asymmetric.
  • EBoth the electronic and vibrational representations must be symmetric.

Q2:

Which of the following would be a spin-allowed transition?

  • A3T13A2
  • B1A23A2
  • C5E2E
  • D3T11T1
  • E4T22T4

Q3:

The chlorophyll molecule possesses a singlet ground state 1T. Which of the following is true?

  • AEmission of light does not obey the Franck–Condon principle.
  • BFluorescence occurs due to a ST transition.
  • CPhosphorescence is a spin-forbidden transition.
  • DPhosphorescence occurs over the same timescale as fluorescence.
  • EFluorescence occurs due to a ST transition.

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