Energy level diagram, fluorescence

Fluorescence is a process that occurs after excitation of a molecule with light. It involves transitions of the outermost electrons between different electronic states of the molecule, resulting in emission of a photon of lower energy than the previously absorbed photon. This is represented in the Jablonski diagram (see Fig. 6.1). As every molecule has different energy levels, the fluorescent properties vary from one fluorophore to the other. The main characteristics of a fluorescent dye are absorption and emission wavelengths, extinction... 

FIGURE 8.11 An energy level diagram depicting the phenomenon of fluorescence in a molecule or complex ion. 

Is the wavelength of fluorescence longer or shorter than the wavelength of absorption Explain your answer with the help of an energy level diagram. 

Figure 4.4 Energy-level diagram showing how the electronic and vibrational energy levels in the ground-state (S0) and first excited-state (Si) anthracene molecule are related to the absorption and fluorescence emission spectra...

A simple energy-level diagram (Figure 4.4) shows that we would expect the 0-0 bands for fluorescence and absorption to occur at the same wavelength, since the energy changes (represented by the lengths of the arrows) are equal. 

Figure 2.5. Energy level diagram (top) and spectra (bottom) illustrating the two-state model of relaxation. The energy of the absorbed quantum is Av , and the energies of the emitted quanta are hvfl (unrelaxed) and hvF (relaxed). The fluorescence spectrum of the unrelaxed state (solid curve) is shifted relative to the absorption spectrum (dotted curve) due to the Stokes shift. The emission intensity from the unrelaxed state decreases and that from the relaxed state (dashed curve) increases as a result of relaxation.

Figure 7.1 Energy level diagram Illustrating changes that occur in IR, normal Raman, resonance Raman, and fluorescence. Notation on the figure stands for Rayleigh scattering (R), Stokes Raman scattering (S), and anti-Stokes Raman scattering (A). Reprinted from Ferraro et al. (2003) [4] with permission from Elsevier.

Fig. 9. a) Absorption and fluorescence spectra of 3,3 -diethylthiadicarbocyanine in methanol b) Corresponding energy level diagram. The lengths of the absorption and fluorescence arrows correspond to the energy of a ruby photon. (From Ref. 1>)... 

The fluorescence and phosphorescence spectra of a complex molecule are generally discussed by reference to an energy level diagram such as that shown in Figure 1. Absorption of light raises the molecule from the ground state to one of the upper electronically excited singlet states. At... 

Energy-level diagram outlining the fluorescence process. 

Fig. 13, Energy level diagram representation of the excitations by (a) Auger electron emission and (b) X-ray fluorescence.

Figure 2.30. Schematic energy-level diagrams depicting the pump-probe (a) OODR and (b) OODR-fluorescence depletion (OODR-FD) experiments. The y and z directions denote the polarization vectors of the various transitions. (Reprinted with permission from Ref. [49].)...

Deposition of HgS on the CdS core on the other hand was shown to yield a variety of interesting fluorescence properties [275,279]. The charge recombination in such a composite system is modulated by controlling the deposition of HgS. The energy-level diagram describing these possibilities is illustrated in Fig. 13. 

Fig. 1. On the left is a simplified energy-level diagram for l Hg+. The 281.5 nm quadrupole "clock" transition can be observed by monitoring the 194 nm fluorescence. If the ion has made a transition from the Si to the 5/2 level the 194 nm flourescence disappears. For the figure on the right, on the horizontal axis is plotted the relative detuning from line center in frequency units at 281.5 nm. On the vertical axis is plotted the probability that the fluorescence from the 6s Si - 6p pi first resonance transition, excited by laser radiation at 194 nm, is on immediately after the 281.5 nm pulse. The electric-quadrupole-allowed S-D transition and the first-resonance S-P transition are probed sequentially in order to avoid light shifts and broadening of the narrow S-D transition. The recoilless absorption resonance or carrier (central feature) can provide a reference for an optical frequency standard. (From ref. 11)...

Fig. 1. Schematic energy level diagram for fluorescence and dissociation of some polyatomic molecules. A0 to X are vibration levels of the normal electronic state. Y to Y are the vibration levels of the electronic (singlet) state formed by absorption. Zo to Zm are vibration levels of the long lived (triplet) electronic state. Fluorescence occurs by transition to X levels from F0 to Za. Dissociation is possible at higher energies than D (Noyes98).

Figure 11.23. Energy level diagram and observed transitions for SrF in its X2 + state, showing the 19F hyperfine splitting [43], observed because of the higher resolution obtained with the microwave/optical polarisation method. This diagram may be compared with figure 11.21, appropriate for the earlier lower resolution studies employing conventional fluorescence detection.

Figure 11.41. Energy level diagrams and transitions for two different F-branch transitions in the YS molecule. The broken lines denote laser-induced fluorescence transitions, whilst the continuous lines indicate radiofrequency double resonance transitions observed in rotational levels of the ground electronic state [82].

Fig. 32 Typical energy level diagram illustrating the photophysical processes that take place upon local excitation of the donor chromophore (a similar scheme obtains for excitation of the acceptor chromophore). kd represents both radiative (fluorescence) and non-radiative decay processes.

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