Time-resolved spectroscopy characteristics

The steady-state luminescence of water-organic complexes is strong and conceals the weaker characteristic luminescence of uranium containing centers, which can be detected by the difference in decay times only. The reason is that the decay time of water-organic complexes is characterized by two time intervals less then 30 ns and more then 10 ms. Since the uranium centers have decay times in the microseconds range, it is possible to detect them by time-resolved spectroscopy. In the time-delayed laser-induced spectroscopy, the luminescence spectra are recorded at a fixed moment after a laser pulse. These spectra maybe different from the integrated steady-state ones since after a certain time short luminescence will be practically absent. 

It is well known that both nanometre and nanosecond-picosecond resolutions at an interface can be achieved by total internal reflection (TIR) fluorescence spectroscopy. Unlike steady-state fluorescence spectroscopy, fluorescence dynamics is highly sensitive to microscopic environments, so that time-resolved TIR fluorometry at water/oil interfaces is worth exploring to obtain a clearer picture of the interfacial phenomena [1]. One of the interesting targets to be studied is the characteristics of dynamic motions of a molecule adsorbed on a water/oil interface. Dynamic molecular motions at a liquid/liquid interface are considered to be influenced by subtle changes in the chemical/physical properties of the interface, particularly in a nanosecond-picosecond time regime. Therefore, time-resolved spectroscopy is expected to be useful to study the nature of a water/oil interface. 

The technique of representing the intensities of spectral lines as a function of time is referred to as time-resolved spectroscopy. Time resolution of spectroscopic information has been applied to many problems, such as the kinetics of fast decay phosphorus, radiation from fast photolysis sources, and exploding wire phenomena. Of most importance to analytical spectroscopy is the use of time-resolved spectroscopy to study the characteristics of ac spark and ac arc discharges of the type normally used for analytical emission spectral analysis, since such information may be useful in optimizing operating conditions. 

In this study, we adopted two kinds of fluorescence spectroscopy, steady-state and the time-resolved spectroscopy in the picosecond time range, for the analysis of energy flow in whole cells of the marine dinoflagellate Protogonyalux tamarensis under the excitation condition of peridinin. Results show unique fluorescence components in this species and characteristic energy flow among them. 

In the proposed book there is an emphasis cm luminescence lifetime, which is a measure of the transition probability and non-radiative relaxation from the emitting level. Luminescence in minerals is observed over a time interval of nanoseconds to milliseconds. It is therefore a characteristic and a unique property and no two luminescence emissions will have exactly the same decay time. The best way for a combination of the spectral and temporal nature of the emission can be determined by time-resolved spectra. Such techniques can often separate overlapping features, which have different origins and therefore different luminescence lifetimes. The method involves recording the intensity in a specific time window at a given delay after the excitation pulse where both delay and gate width have to be carefully chosen. The added value of the method is the energetic selectivity of a laser beam, which enables to combine time-resolved spectroscopy with powerful individual excitation. 

Other studies utilizing (nanosecond) time-resolved spectroscopy have been carried out on ion pairs, such as those based on donors consisting of Zn, Cd, and Hg bis-dithiolene anions and bipyridinium dications (viologens) [192-194] as acceptors (e.g., methylviologen with Ered° = - 0-41 V). These salts give rise to the characteristic bands of the reduced viologen (MV +, max = 391 and 608 nm) and that of the oxidized dithiolene complex (Xmax = 450 nm), e.g. 

Coupling between molecular processes and morphological changes is one of the most unique and important characteristics of laser ablation. Excitation energy relaxation dynamics and primary chemical processes of organic molecules in laser ablation have been investigated by using various time-resolved spectroscopies, such as fluorescence, absorption, Raman and IR spectroscopies. Laser ablation leads to rapid temperature elevation of the polymer matrix and thermal decomposition of the polymer. Ablation causes not only photochemical reactions but also photo-initiated thermal reactions. 

The purpose of this chapter is to review ultrafast, time-resolved X-ray diffraction from liquids. Both experimental and theoretical problems will be treated. The stmcture of the chapter is as follows. Section II describes the principles of a time-resolved X-ray experiment and details some of its characteristics. Basic elements of the theory are discussed briefly in Sections III-V. Finally, Section VI presents recent achievements in this domain. The related field of time-resolved X-ray spectroscopy, although very promising, wiU not be discussed. 

Normally, time-resolved FT-IR spectroscopy (TRS FT-IR) possesses the same data characteristics. In a typical TRS FT-IR experiment, interferograms are assembled for a specific delay time after the photolysis pulse, and the data produced are normally finer-grained in frequency than in time. This type of experiment is complementary to experiments with fine-grained time information. It is particularly useful where a wide spectral range is necessary and works reasonably well for highly reproducible events which occur on relatively long timescales (fractions of seconds) (83). It is also an appealing system for use on shorter timescales, and it has... 

The historical development and elementary operating principles of lasers are briefly summarized. An overview of the characteristics and capabilities of various lasers is provided. Selected applications of lasers to spectroscopic and dynamical problems in chemistry, as well as the role of lasers as effectors of chemical reactivity, are discussed. Studies from these laboratories concerning time-resolved resonance Raman spectroscopy of electronically excited states of metal polypyridine complexes are presented, exemplifying applications of modern laser techniques to problems in inorganic chemistry. 

A. Itaya, T. Yamada, K. Tokuda, and H. Masuhara, Interfacial characteristics of poly(methyl methacrylate) film Aggregation of pyrene and micropolarity revealed by time-resolved total internal reflection fluorescence spectroscopy, Polym. J. 22, 697-704 (1990). 

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). 

Characteristic bands of Mn + well studied by steady-state luminescent spectroscopy (Tarashchan 1978 Gorobets and Rogojine 2001) have been found in time-resolved luminescence spectra of calcite (Fig. 4.14a), fluorite (Fig. 4.10d), datolite (Fig. 4.16d), wollastonite (two bands at 555 and 603 nm Fig. 4.42a,c), and spodumen (Fig. 4.61a). 

TCLP TDB TDF THC TBP TEM TLM TM-AFM TOC TRLFS TRU TSP TST TVS Toxicity characteristics leaching procedure Thermodynamic database Tyre-derived fuel Total hydrocarbon Tri-n-butyl phosphate Transmission electron microscopy Triple layer model Tapping mode atomic force microscopy Total organic carbon Time-resolved laser fluorescence spectroscopy Transuranic Total suspended particles Transition state theory Transportable vitrification system... 

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