M C by Kanni Raj A

Author:Kanni Raj, A
Language: eng
Format: azw3
Published: 2016-01-12T16:00:00+00:00

Radiationless Deactivation - When a molecule relaxes without emitting a photon we call the process radiationless deactivation. One example of radiationless deactivation is vibrational relaxation, in which a molecule in an excited vibrational energy level loses energy by moving to a lower vibrational energy level in the same electronic state. Vibrational relaxation is very rapid, with an average lifetime of <10 12 s. Because vibrational relaxation is so efficient, a molecule in one of its

radiationless deactivation is an internal conversion in which a molecule in the ground vibrational level of an excited state passes directly into a higher vibrational energy level of a lower energy electronic state of the same spin state. By a combination of internal conversions and vibrational relaxations, a molecule in an excited electronic state may return to the ground electronic state without emitting a photon. A related form of radiationless deactivation is anexternal conversion in which excess energy is transferred to the solvent or to another component of

adiationless deactivation is an intersystem crossingin which a molecule in the ground vibrational energy level of an excited electronic state passes into a higher vibrational energy level of a lower energy electronic state with a different spin state. For example, an intersystem crossing is shown in Figure 10.48 between a singlet excited state, S1, and a triplet excited state, T1.

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