Absoiption spectra

The vibronic coupling model has been applied to a number of molecular systems, and used to evaluate the behavior of wavepackets over coupled surfaces [191]. Recent examples are the radical cation of allene [192,193], and benzene [194] (for further examples see references cited therein). It has also been used to explain the lack of structure in the S2 band of the pyrazine absoiption spectrum [109,173,174,195], and recently to study the photoisomerization of retina] [196],... 

Furthermore, as shown in Fig. 10.2, such red shifts in the absorption band of the metal ion-implanted titanium oxide photocatalysts can be observed for any kind of titanium oxide except amorphous types, the extent of the shift changing from sample to sample. It was also found that such shifts in the absorption band can be observed only after calcination of the metal ion-implanted titanium oxide samples in 02 at around 723-823 K. Therefore, calcination in 02 in combination with metal ion-implantation was found to be instrumental in the shift of the absoiption spectrum toward visible light regions. These results clearly show that shifts in the absorption band of the titanium oxides by metal ion-implantation is a general phenomenon and not a special feature of a certain kind of titanium oxide catalyst. 

FIG. 3. Estimation of the Sn -Sl absorption spectrum of cresyl violet in ethanol. 1 observed spectrum at 166ps 2 steady state absorption spectrum 3 stimulated fluorescence spectrum 4 superposition of absorption and stimulated fluorescence spectra 5 the Sn -Sl absoiption spectrum. 

Figure 8. The absoiption spectrum of tetramethylethylene in the gas phase. From Ref. 83 with kind permission of the authors.

An absoiption spectrum could be the result of the overlapping of two or more absorption transitions. Separation of each band can be performed by means of the excitation polarization spectnim. If the spectrum consists of regions of constant polarization joined regions of varying polarizalioo, it is possible to consider that one... 

Absoiption spectrum of the complexed poiphyrin is characteristic of the absorption of porphyrin in neutral medium (Fig. 9.13). 

The absoiption spectrum of pure Y2O3 shows only the latter absorption. Therefore the ines and the 250 nm band must be due to Eu. and the absorption at A < 230 nm to the host lattice Y2O3. 

Plot (a) was obtained from an organic dye and plot (b) was obtained from a quantum dot suspension. For an organic dye solution, since the sizes of organic dye molecules are the same and the quantum levels (n) arc well fixed so a distinct absoiption spectrum will be obtained. For a quantum dot suspension, due to the diameter variation of quantum dots and variable quantum transition levels, the separation of energy levels will vary as l /r ). Therefore, the w avelength of light that can cause excitation w ill also vary. 

The first scheme to be treated is based on a frequency modulation of the monochromatic incident wave. It was not designed specifically for laser spectroscopy, but was taken from microwave spectroscopy where it is a standard method. The laser frequency co] is modulated at the modulation frequency which tunes col periodically from col to col + Acol- When the laser is tuned through the absoiption spectrum, the difference It(col) — h ojL + Aojl) is detected with a lock-in amplifier (phase-sensitive detector) tuned to the modulation frequency (Fig. 6.2). If the modulation sweep Acol is sufficiently small, the first term of the Taylor expansion... 

Figure 3-31. Infrared absoiption spectrum of a commercial film of polyethylene before and after subtraction of the spectrum of the defect mode component near 1440 cm . After subtraction of the defect mode the ratio between component a and b of the correlation field splitting approached the ideal value for a setting angle of 42 (see text).

A molecule that undergoes a reversible photoinduced change between two states with different optical properties such as color or absoiption spectrum is considered to be photochromic. The chromogenic effect, photochromism, can be illustrated by the photochemical transformation of molecule A to B upon absorption of light ... 

Figure 2. Absoiption spectrum of calculated with different configuration interaction, case (a) 69 configurations, case (b) 300 configurations and (c) 3000 configurations, in case (c) a counter ion was placed in the ix)sition.

Figure 5. Photoinduced q>tical absoiption spectrum for unoriented Durtiam polyacetylene, (a) measured at 77 K with excitation at 488 nm [48], and (b) measured at 20 K with excitation at 457.9 nm [46].

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