Crystals time-resolved measurements

Time-resolved measurements of photogenerated (very intense illumination, up to 0.56 GW/cm ) electron/hole recombination on CD (selenosulphate/NTA bath) CdSe of different crystal sizes has shown that the trapping of electrons, probably in surface states, occurs in ca. 0.5 ps, and a combination of (intensity-dependent) Auger recombination and shallow-trapped recombination occurs in a time frame of ca. 50 ps. A much slower (not measured) decay due to deeply trapped charges also occurred [102]. A different time-resolved photoluminescence study on similar films attributed emission to recombination from localized states [103]. In particular, the large difference in luminescence efficiency and lifetime between samples annealed in air and in vacuum evidenced the surface nature of these states. 

In the above experiments in which an electrode surface is examined, the electrode potential is fixed as the electrode surface is rotated and the SH anisotropy recorded. In a useful variation of this procedure, one can fix the angle of rotation and measure the SH response as a function of potential. Since the absolute orientation of the crystal is known, information can be derived about the various tensor elements describing the nonlinear polarizability from these crystalline surfaces. By fixing the angle and applying a transient potential pulse, one can perform time resolved measurements and watch the evolution of various adsorption and deposition processes along specific crystal axes. 

Brennan C, Nelson KA. Direct time-resolved measurement of anharmonic lattice vibrations in ferroelectric crystals. J Chem Phys 1997 107 9691-9694. 

Fig. 6.21 Sensitised fluorescence of anthracene doped with 2.3 10 mol/mol of tetracene, at 1.6 K in a time-resolved measurement. The two-photon excitation was carried out with a lOps pulse of wavelength 614.5 nm. It was chosen in order to excite the bulk of the crystal as homogeneously as...

For pico- and femtosecond studies, time-resolved measurements require powerful pulsed laser systems operated in conjimction with effective detection techniques. Relevant commercially available laser systems are based on Ti sapphire oscillators, tunable between 720 and 930 nm (optimum laser power around 800 nm). For nanosecond work, Nd iYAG (neodymium-doped yttrium-alumi-num-gamet) (1064 nm) and ruby (694.3 nm) laser systems are commonly employed. For many applications, light pulses of lower wavelength are produced with the aid of appropriate nonlinear crystals through second, third, or fourth harmonic generation. For example, short pulses of 2=532, 355, and 266 nm are generated in this way by means of Nd " YAG systems. Moreover, systems based... 

Oriented PET in the glassy states is a useful system when investigating the effect of orientational order on polymer crystallization mechanism. The crystallization rate of PET is slow enough for time-resolved measurements to... 

Maeda et al. (2002) have developed a crystal spectrometer system for rapid chemical state analysis by external beam particle-induced X-ray emission. The system consists of a flat single crystal and a five-stacked position sensitive proportional counter assembly. Chemical state analysis in atmospheric air within several seconds to several minutes is possible. A mechanism for time-resolved measurements is installed in the system. Performance of the system is demonstrated by measuring the time-dependence of chemical shifts of sulfur Kai 2 line from marine sediment and aerosol samples. Earlier, Maeda et al. (1999) used a flat analyzing crystal and a position sensitive proportional counter to measure line shifts (with the precision of 0.1 eV) of Si Ka and P Ka X-rays from various samples for chemical state analysis of minor elements. 

Wasanasuk K, Tashiro K (2011) Structural regularization in the crystallization process from the glass or melt of poly(l-lactic acid) viewed from the temperature-dependent and time-resolved measurements of FTIR and wide-angle/small-angle X-ray scatterings. Macromolecules... 

Recently the luminescence properties of Pr ", Nd, Tm and Yb " ions in fluorite have been obtained by steady-state measurements. In addition, the luminescence spectra of Ce ", Sm ", Sm ", Dy ", Er and Yb were measured. It was pointed out that Xex = 415 nm is most suitable for measuring the Ho " emission beside the Er ". The emission of trivalent holmium and erbium ions was measured independently using time-resolved measurements and tentative assignment of luminescence lines to 3 and C4V symmetry sites was proposed. Besides for natural fluorite crystal, the transition between Stark energy levels of lanthanide ions were presented (Czaja et al. 2012). 

Infomiation about the synthesis of the PEEK fractions, annealing experiments from the glassy state, crystallization from the melt, analysis by differential scanning calorimetry, WAXD and SAXS experimental setup for static and time-resolved measurements and the treatment of the experimental data can be found in previous papers (25,26,47). 

Difference-frequency laser (cw) (see Section 20.4.2.1 for the generation of difference frequency) By using various nonlinear crystals, this laser can cover almost the entire mid-infrared region (the lower limit is about 550 cm ). Since the width of this laser line is very narrow, this laser is important for performing high-resolution time-resolved measurements in the gaseous state. 

This time-resolved measurement method can be applicable to relatively slow transient phenomena, as its time-resolved measurements are undertaken while the movable mirror is at rest. The number of applications of step-scan FT-IR spectrometry to time-resolved measurements currently is more than that by any other method, and it has been applied to various studies in many fields such as studies of biomolecules, liquid crystals, polymers, photochemical reactions in zeolites, oxidation-reduction reactions on electrode surfaces, and excited electronic states of inorganic complexes. Further, this method has been applied to time-resolved measurements in combination with attenuated total reflection (ATR) (see Chapter 13), surface-enhanced infrared absorption (see Section 13.2.2) [10, 11], infrared microscopic measurements (see Chapter 16) [12], and infrared spectroscopic imaging (see Chapter 17) [13]. 

Tashiro, K., Ueno, Y, Yoshioka, A., Kobayashi, M. Molecular mechanism of solvent-induced crystallization of syndiotactic polystyrene glass. 1. Time-resolved measurements of infrared/Raman spectra and X-ray diffraction. Macromolecules,... 

Generation of Disordered Phase in Isothermal Crystallization of Polyethylene We perform a similar experiment for PE. Figure 5.17 shows the time-resolved measurement of infrared spectra in the isothermal crystallization process from the melt, where we use a linear low-density PE with 17 ethyl branches per... 

Lantz J M and Corn R M 1994 Time-resolved optical second harmonic generation measurements of picosecond band flattening processes at single crystal TiO, electrodes J. Phys. Chem. 98 9387-90... 

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