Time-resolved luminescence spectroscopy

One example demonstrates the advantage of the time-resolved technique compared to the steady-state technique. The time-integrated cathodolumines-cence spectrum of apatite enables us to detect only two dominant luminescence 

The optical setup for time-resolved micro-luminescence measurements is based around an Axiotech 100 HD Zeiss microscope, modified to allow laser injection and fluorescence collection. The sample is observed either under transmission or reflection of polarized white light, or under UV illumination (HBO lamp). A set-up consisting of a dichroic mirror, for the selection of the excitation wavelength, and an objective (Epiplan Neofiuar obj. 350 nm Ealing/Coherent reflection obj. 350 nm) is used to focus the laser beam on the sample (spatial resolution over 5 pm with a x50 objective). The lim- 

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Molecular Studies on Laser Ablation Processes of Polymeric Materials by Time-Resolved Luminescence Spectroscopy... 

Time-resolved luminescence spectroscopy may be extremely effective in minerals, many of which contain a large amount of emission centers simultaneously. With the steady state technique only the mostly intensive centers are detected, while the weaker ones remain unnoticed. Fluorescence in minerals is observed over time range of nanoseconds to milliseconds (Table 1.3) and this property was used in our research. Thus our main improvement is laser-induced time-resolved spectroscopy in the wide spectral range from 270 to 1,500 nm, which enables us to reveal new luminescence centers in minerals previously hidden by more intensive centers. 

Fig. 3.1. Schematic experimental setup for time-resolved luminescence spectroscopy...

After a delay of several ps, the luminescence of Eu " is already very weak, and narrow long-lived lines of trivalent RE dominate in the spectrum. The lines at 589, 617, 651, and 695 nm (Fig. 4.1c) have never been detected in natural apatite by steady-state spectroscopy. According to their spectral position they may be ascribed to Eu ", but they are different from known lines in synthetic apatites activated by Eu (Jagannathan and Kottaosamy 1995 Morozov et al. 1970 Piriou et al. 1987 Piriou et al. 2001 Voronko et al. 1991). In order to clarify this problem we studied artificially activated samples by laser-induced time-resolved luminescence spectroscopy. 

Time-resolved luminescence spectroscopy of zircon revealed luminescence lines, which maybe confidentially ascribed to a Eu center (Fig. 4.38d). Usually they are hidden by a broad band yellow emission of zircon and may be detected only with a long delay time using its much longer decay time compared to yellow luminescence. 

Time-resolved luminescence spectroscopy of sodalite evidences that the vibration structure has a very short decay time and disappears after a delay of 250 ns. Such structure is superimposed on the very broad IR band (Fig. 4.65). 

The violet emission of the radiation-induced center (COs) " is well known in steady-state luminescence spectra of calcite (Tarashchan 1978 Kasyanenko, Matveeva 1987). The problem is that Ce also has emission in the UV part of the spectrum. In time-resolved luminescence spectroscopy it is possible to differentiate between these two centers because of the longer decay time of the radiation-induced center. Its luminescence peaking at 405 nm becomes dominant after a delay time of 100-200 ns while emission of Ce is already quenched (Fig. 4.14f). 

In 2004, Zhang and coworkers reported the first experimentally observed example of case (b) in Figure 1.8 by means of time-resolved luminescence spectroscopy with the system shown in Figure 1.9. 

Time-resolved luminescence spectroscopy complements the steady-state method and can provide essential kinetic information about the decay of excited states. Application of time-resolved fluorescence spectroscopy for analytical chemistry, where low concentrations might require the use of long... 

Molecular photophysics, especially the use of steady-state and time-resolved luminescence spectroscopy, have many important applications and there has been a progressive emergence of a new field of analytical chemistry based on these principles. It has been known for many decades that the excited state properties of certain molecules are highly sensitive to the local environment but it is only recently that a concerted effort has been made to use this sensitivity in a practical way. The main approaches to employing variations in photophysical properties as an analytical tool can be divided into two areas namely, (i) development of luminescent probes that respond to changes in the environment and (ii) identification of molecular systems for which the emission... 

In our opinion the paper by Moses et al. [36] on the scintillation mechanisms in CeF.3 is a fine example of how scintillators should be studied from a fundamental point of view. A combination of techniques was u.sed, viz. (time-resolved) luminescence spectroscopy, ultraviolet photoelectron spectroscopy, transmission spectroscopy, and the excitation region was extended up to tens of eV by using synchrotron radiation. Further, powders as well as crystals with composition Lai-xCexFy were investigated,... 

The products of PLASLA in the gaseous CU-CF4 system are found to be polymeric carbon materials by time-resolved luminescence spectroscopy [Tanaka et al., 2003a, 2003b, 2004] and TOF (time-of-flight) mass spectrometry [Takenaka et al. unpublished data, Nakano et al., 2010]. Since various polymeric carbon materials have been extensively used for manufactures, PLASLA will be very promising in industry, as well as materials science. 

The PLASLA products materials will be discussed more in detail with the results of the TOP mass spectrometry and Time-resolved luminescence spectroscopy measurements [Takenaka et al., unpublished data]. 

Time-resolved luminescence spectroscopy studies have been started approximately 20 years ago and the main results are presented by Gaft et al. (2005) and Panczer (2001). The task of our present paper is to present the main new data on luminescence spectroscopy of minerals, which have been received after this book publication both by our groups and by other researches. 

Visible luminescence of many centers, such as Cr ", Mn " and Ni ", has been found and interpreted in the visible range in synthetic forsterite excited with electrons and laser. The polarized absorption spectra and time-resolved luminescence spectroscopy of Cr"activated forsterite led to the discovery of at least two different kinds of Cr " emitting centers (Moncorge et al. 1991) that correspond to Cr " ions in two different sites of six-fold coordination. There are Cr " ions, probably substituting for Mg " ions in both the Ml and M2 sites, which form medium-field systems giving rise to " E-" T2 sharp line emissions at low temperatures with millisecond lifetimes around 700 nm and " T2, thermalized short-... 

Gaft M, PanczCT G (2013) Lasta- induced time resolved luminescence spectroscopy of minerals - a powerful tool for stedying the nature of emission centers. Miner Petrol 107 363-372 Gaft M, Vorontsova L (1982) Luminescence of cassiterite and the possibilities of its practical use. Miner J4(5) 75-78... 

Laser-induced time-resolved luminescence spectroscopy presents a good opportunity to detected different valence states of europium and its different positions inside minerals lattice (Gaft et al. 2001b, 2005). 

Time-resolved luminescence spectroscopy of zircon revealed luminescence lines, which may be confidentially ascribed to Eu center (Fig. 4.90d). Usually they are hidden by broadband yellow emission of zircon and may be detected only with long delay time using its much longer decay time compared to yellow luminescence, fii order to interpret detected those lines time-resolved luminescence of synthetic ZrSi04 activated by Eu was studied (Gaft et al. 2000c) (Fig. 5.13). Time-resolved luminescence spectroscopy enabled to detect at least two Eu centers with different decay times main line 616 nm and much weaker lines at 593 and 702 nm with relatively short decay time, and main lines at 596 and 707 nm and weaker line at... 

The N3 optical center is one of the best known in steady-state luminescence spectra diamond. It is connected with three substitutional nitrogen atoms botmded to a common carbon atom or a vacancy, the ground state being a level and the excited state where luminescence originates a state (C3V point group). The zero-phonon line occurs at 2.985 eV and absorption and emission spectra show very closely a mirror relationship (Bokii et al. 1986). The N3 prompt luminescence decay is exponential and equal to 40 ns. Time-resolved luminescence spectroscopy enables to detect that N3 center has some metastable levels between the emitting and ground state. One of the decay paths of these metastable levels is delayed N3 luminescence, which occurs... 

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