Spectroscopy excitation spectrum

Figure 8. Optical spectroscopy of a indocyanine green dye solution (10 5 M in water) (a) fluorescence spectrum obtained by excitation around 780 nm (b) excitation spectrum obtained on top of a microresonator the rectangle in the inset shows the area from which the fluorescence signal is collected.

The most notable feature of these intrazeolite photooxygenations (Fig. 30) is that the oxygen CT band experiences a dramatic bathochromic shift in comparison to solution. This was detected initially by recording the product growth as a function of irradiation wavelength (laser reaction excitation spectrum)98,110 and was later verified by direct observation using diffuse reflectance UV-Vis spectroscopy.111 For example, 2,3-dimethyl-2-butene CT-absorbance is shifted to lower energy by more than 300 nm... 

More sensitive than ESA is so-called excited state excitation (ESE), by using fluorescence spectroscopy. In this case, the excitation spectrum corresponding to an... 

The excitation spectrum demonstrates that for an effective luminescence not only the presence of an emitting level is important, but also the presence of the upper levels with a sufficiently intensive absorption. The excitation spectra enable us to choose the most effective wavelength for luminescence observation. The combination of excitation and optical spectroscopies enable us to determine the full pattern of the center s excited levels, which may be crucial for luminescence center interpretation, energy migration investigation and so on. The main excitation bands and fines of luminescence in minerals are presented in Table 2.2. 

Two types of Ce centers in calcite were detected by steady-state spectroscopy (Kasyanenko and Matveeva 1987). The first one has two bands at 340 and 370 nm and is connected with electron-hole pair Ce -COj". The second one has a maximum at 380 nm and was ascribed to a complex center with Ce and OH or H2O as charge compensators. Such a center becomes stronger after ionizing irradiation and disappears after thermal treatment. The typical example of Ce luminescence in the time-resolved liuninescence of calcite consists of a narrow band at 357 nm with very short decay time of 30 ns, which is very characteristic for Ce " (Fig. 4.13a). It was found that Ce " excitation bands occurs also in the Mn " " excitation spectrum, demonstrating that energy transfer from Ce to Mn " occurs (Blasse and Aguilar 1984). 

The Introduction chapter contains the basic definitions of the main scientific terms, such as 5pectro5copy, luminescence spectroscopy, luminescent mineral, luminescent center, luminescence lifetime, luminescence spectrum and excitation spectrum. The state of the art in the steady-state luminescence of minerals field is presented. The main advantages of the laser-induced time resolved technique in comparison with the steady-state one are shortly described. 

Figure 18-21 Excitation and emission spectra of anthracene have the same mirror image relation as the absorption and emission spectra in Figure 18-16. An excitation spectrum is nearly the same as an absorption spectrum. [C. M. Byron and T. C. Wemer. Experiments in Synchronous Fluorescence Spectroscopy lor the Undergraduate Instrumental Chemistry Course"...

Increasing the solvent polarity results in a red shift in the -t -amine exciplex fluorescence and a decrease in its lifetime and intensity (113), no fluorescence being detected in solvents more polar than tetrahydrofuran (e = 7.6). The decrease in fluorescence intensity is accompanied by ionic dissociation to yield the t-17 and the R3N" free radical ions (116) and proton transfer leading to product formation (see Section IV-B). The formation and decay of t-17 have been investigated by means of time resolved resonance Raman (TR ) spectroscopy (116). Both the TR spectrum and its excitation spectrum are similar to those obtained under steady state conditions. The initial yield of t-1 is dependent upon the amine structure due to competition between ionic dissociation and other radical ion pair processes (proton transfer, intersystem crossing, and quenching by ground state amine), which are dependent upon amine structure. However, the second order decay of t-1" is independent of amine structure... 

The 1 isomer is difficult to detect and identify by IR spectroscopy, since the IR spectrum only contains one weak line. In contrast, there are two transitions of intermediate strength in the Raman spectrum, and consequently Raman spectroscopy can be used for identification without the need of isotopic labeling. An alternative approach for detection is LIF spectroscopy. Excited state calculations, using linear and quadratic CCSD theory, indicates that the... 

Figure 12-1. Schematic diagram to illustrate double resonance techniques, (a) REMPI 2 photon ionization. The REMPI wavelength is scanned, while a specific ion mass is monitored to obtain a mass dependent SI <- SO excitation spectrum, (b) UV-UV double resonance. One UV laser is scanned and serves as a burn laser, while a second REMPI pulse is fired with a delay of about 100 ns and serves as a probe . The probe wavelength is fixed at the resonance of specific isomer. When the burn laser is tuned to a resonance of the same isomer it depletes the ground state which is recorded as a decrease (or ion dip) in the ion signal from the probe laser, (c) IR-UV double resonance spectroscopy, in which the burn laser is an IR laser. The ion-dip spectrum reflects the ground state IR transitions of the specific isomer that is probed by the REMPI laser, (d) Double resonance spectroscopy can also use laser induced fluorescence as the probe, however that arrangement lacks the mass selection afforded by the REMPI probe...

Another method of measuring the relative quantum yield of the radical decomposition process (eq. 22) was also devised recently (144). This involves HNO chemiluminescence photoexcitation spectroscopy. When an H atom recombines with an NO molecule, an electronically excited HN0 ( A A" ) is formed. Fluorescence emission from HNO occurs at 762 nm. The HNO chemiluminescence in a low-pressure 1 10 mixture of H2CO and NO is proportional to the H-atom quantum yield from the photolysis of H2CO. The photoexcited HNO (red) chemiluminescence excitation spectrum of a H2CO/NO mixture obtained with a tunable laser at high resolution is shown in Fig. 2 together with an absorption spectrum and a H2CO fluorescence (blue) excitation spectrum (237). The relevant reaction scheme is as follows ... 

The laser-excited fluorescence from dibenzofuran in a biphenyl host at 4.2 K and three different sites in the lattice have been identified. The two-photon excitation spectrum of single crystals of carbazole at 4.2 K has been analysed in detail. Very extensive vibrationally unrelaxed fluorescence is observed following dye-laser excitation of single vibronic levels of naphthazanine and the rates and pathways of relaxation are examined by picosecond emission spectroscopy. The photophysics of rubrene peroxide have been measured for the first time by Bayrakceken. Picosecond fluorescence has been used to study the spectra and kinetics for Sj— So and Si transitions for... 

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