Consider the following statements regarding the processes of fluorescence and phosphorescence. Determine whether each statement is true for fluorescence only, true for phosphorescence only, true for both processes, or true for neither process.
a) The energy of the absorbed photon equals the energy of the emitted photon.
b) Photon absorption usually occurs when a molecule is in an excited triplet electronic state.
c) The lifetime of the excited vibrational states is about a femtosecond; the lifetime of the excited electronic state is generally longer than a nanosecond.
d) Vibrational relaxation is a non-radiative process.