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Fluorescence and Phosphorescence Quiz

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Questions and Answers

What are the two triplet electronic states involved in the Perrin–Jablonski diagram?

T1, T2

What is the process in which a part of energy absorbed by a substance is released in the form of light?

Fluorescence

What is the characteristic lifetime of the excited states for fluorescence?

10^-10 - 10^-7 seconds

From which type of excited states does fluorescence emission take place?

Singlet Signup and view all the answers

What type of excitation can bring a molecule to one of the vibrational levels of S1 or S2?

Absorption of a photon Signup and view all the answers

What type of transition is responsible for delayed fluorescence?

Triplet-triplet transitions Signup and view all the answers

What is the mirror image rule in the context of absorption and fluorescence spectra?

The emission spectrum often appears to be symmetrical to the absorption spectrum. Signup and view all the answers

Why do most fluorescent molecules exhibit broad and structureless absorption and emission bands?

Because each electronic state consists of an almost continuous manifold of vibrational levels. Signup and view all the answers

In what case can the absorption spectrum partially overlap the fluorescence spectrum?

When the excitation occurs from a vibrational excited level of the S0 state. Signup and view all the answers

What is the probability of finding a molecule in the S1 state at room temperature due to thermal energy?

Nearly zero. Signup and view all the answers

What is the process of vibrational relaxation?

The energy deposited by the photon into the electron is given away to other vibrational modes as kinetic energy. Signup and view all the answers

Why is internal conversion from S2 to S1 more efficient than from S1 to S0?

Because of the much larger energy gap between S1 and S0. Signup and view all the answers

What is intersystem crossing in the context of electronic states?

A non-radiative transition between two isoenergetic vibrational levels belonging to electronic states of different multiplicities. Signup and view all the answers

What is the likelihood of intersystem crossing compared to internal conversion?

Intersystem crossing is less efficient than internal conversion. Signup and view all the answers

What is the outcome of vibrational relaxation when a molecule is excited to a level higher than the lowest vibrational level of the first electronic state?

It leads the excited molecule towards the lowest vibrational level (v = 0) of the S1 singlet state. Signup and view all the answers

What is internal conversion, and why does it occur?

Internal conversion is a non-radiative and isoenergetic transition between two electronic states of the same spin multiplicity. Signup and view all the answers