Time-resolved profile

Figure 1. Time-resolved profiles of cations from the + C2H6 reaction at 2.0-eV collision energy. The decay of CDj and the formation of C2H5 and CD3CH2 cations follow pseudo-first-order kinetics. Reprinted from [38] with permission from Elsevier.

Note that the usage of 10-fs laser pulse leads to rich oscillatory components as well as these rapid kinetics in their pump-probe time-resolved profiles. Obviously in this timescale, the temperature T will have no meaning except for the initial condition before the pumping process. In addition, such oscillatory components may be due not only to vibrational coherence but also to electronic coherence. A challenging theoretical question may arise, for such a case, as to how one can describe these ultrafast processes theoretically. 

From the above discussion, we can see that the purpose of this paper is to present a microscopic model that can analyze the absorption spectra, describe internal conversion, photoinduced ET, and energy transfer in the ps and sub-ps range, and construct the fs time-resolved profiles or spectra, as well as other fs time-resolved experiments. We shall show that in the sub-ps range, the system is best described by the Hamiltonian with various electronic interactions, because when the timescale is ultrashort, all the rate constants lose their meaning. Needless to say, the microscopic approach presented in this paper can be used for other ultrafast phenomena of complicated systems. In particular, we will show how one can prepare a vibronic model based on the adiabatic approximation and show how the spectroscopic properties are mapped onto the resulting model Hamiltonian. We will also show how the resulting model Hamiltonian can be used, with time-resolved spectroscopic data, to obtain internal... 

We consider a model for the pump-probe stimulated emission measurement in which a pumping laser pulse excites molecules in a ground vibronic manifold g to an excited vibronic manifold 11 and a probing pulse applied to the system after the excitation. The probing laser induces stimulated emission in which transitions from the manifold 11 to the ground-state manifold m take place. We assume that there is no overlap between the two optical processes and that they are separated by a time interval x. On the basis of the perturbative density operator method, we can derive an expression for the time-resolved profiles, which are associated with the imaginary part of the transient linear susceptibility, that is,... 

A pumping laser excites the system from the ground vibronic manifold g to the excited vibronic manifold n. After excitation, a probing laser is applied to induce transitions from the manifold to the manifold g via stimulated emission and/or to higher excited manifolds via induced absorption. This work shall focus on the pump-probe time-resolved stimulated emission experiment. In this case, an expression for the time-resolved profiles is derived in terms of the imaginary part of the transient susceptibility X (copu,copr, x). In the adiabatic approximation and the Condon approximation, it has been shown that [18,21]... 

Previous SNOM measurements have been performed by detecting the fluorescence signal from the specimen in many cases. Fluorescence SNOM is so sensitive that it can detect the signal from a single molecule and provides valuable information such as the orientation and spatial distribution of the fluorescent molecules not only from the intensity but also from the spectra and time-resolved profiles. Needless to say, however, the fluorescence SNOM measurement can be apphed only to the chemical species which is fluorescent in a visible range. For a non-fluorescent specimen, the fluorescence labeling must be carried out, but the introduction of dye molecules often involves complicated chemical synthetic processes. The fluorescence SNOM limits its versatility in variation of observable species, while it is... 

Figure 4.2.2. Normalized time-resolved profiles of an apple and its cuticle.

The time-resolved profile refers to the variation in intensity of the detected light beam with time. The normalized time-resolved profiles of an apple (89 mm in diameter) and its cuticle (1.0 mm in thickness) are illustrated in Figure 4.2.2. The sampling time and the number of times the transmitted output power was averaged were 100 ns and 300, respectively. The time-resolved profile of the cuticle was conveniently employed as the reference. It is important to focus on some typical parameters representing the variation of the time-resolved profile. For example, variations in peak maxima, the time delay of peak maxima, and the full width at half-maximum of the profile are fundamental optical factors. The measure of attenuance (A,) is defined as follows ... 

TOF-NIRS was introduced to clarify the optical characteristics of wood having a cellular or porous structure as an anisotropic medium. The combined effects of the wood structure, the wavelength of the laser beam, and the detection position of transmitted light on the time-resolved profiles were investigated. In this study, the time-resolved profile of a sample with thickness of 1 mm was taken as a reference. 

Results and Discussion. One of the primary considerations of this study is to show that single-line, single-injection FIA can be used to create non-chromatographic, yet time-resolved profiles for multicomponent analysis. 

The absence of a detectable risetime for the time-resolved profile of excimer fluorescence from a solution of the 2NMA-BDHM copolymer suggests that the residence time of the excitation energy is too short to permit excimer formation by rotational reorientation of chromophores. This short residence time is attributed to efficient competition for the excitation energy by rapid one-step energy transfer to a benzotriazole trap and suggests that the excimer fluorescence originates from excimer sites which are formed prior to excitation. 

Figure 7.7 Panel (a) time-resolved emission profiles of acetaldehyde, ethanol and acetone from M. Smegmatis cultures during growth (filled circles) and medium alone (empty triangles). Panel (b) time-resolved profiles of acetaldehyde, ethanol and acetone before and after the addition of ciprofloxacin at t = 29 hours. The resistant strain B shows the same behaviour with and without ciprofloxacin, while the sensitive strain A shows a reduction in the rate of decrease in emissions when compared with the resistant strain B. Reproduced from [17] with permission from Elsevier.

Figure Bl.9.13. Time-resolved SAXS profiles diirmg isothennal crystallization (230 °C) of PET (the first 48 scans were collected with 5 seconds scan time, the last 52 scans were collected with 30 seconds scan time) calculated correlation fiinctions j(r) (nonnalized by the invariant 0 and lamellar morphological variables...

Verma N 0 and Fessenden R W 1976 Time resolved ESR spectroscopy. IV. Detailed measurement and analysis of the ESR time profile J. Chem. Phys. 65 2139-60... 

The objective in these gauges is to measure the time-resolved material (particle) velocity in a specimen subjected to shock loading. In many cases, especially at lower impact pressures, the impact shock is unstable and breaks up into two or more shocks, or partially or wholly degrades into a longer risetime stress wave as opposed to a single shock wave. Time-resolved particle velocity gauges are one means by which the actual profile of the propagating wave front can be accurately measured. 

Figure 8.5. Representative time-resolved stress or particle velocity profiles illustrating features critical to the spall analysis.

The unloading wave itself provides a direct measure of the strength at pressure from the shape of the release wave. Such a measurement requires time-resolved detection of the wave profile, which has not been the usual practice for most strong shock experiments. 

It should be observed that, in the most general case, interpretation of the mechanical responses requires time-resolved wave-profile measurements. As shown in Eqs. (2.2) and (2.3), direct evaluation of the response requires quantitative description of derivatives of kinetic and kinematic variables. 

Fig. 2.17. Fused quartz is known to have an anomalous softening with stress or pressure in both static and shock loading. The time-resolved wave profile measured with a VISAR system shows the typical low pressure ramp followed by a shock at higher pressure. The release to zero pressure is with a shock, in agreement with the shape of the pressure-volume curve (after Setchell [88S01]).

Fig. 2.20. The release wave portion of time-resolved velocity profiles in porous aluminum is shown as measured with VISAR instrumentation. At pressures near that required to cause melt, the release changes from that of an elastic wave to that of a bulk plastic wave, indicating the change to a melt condition (after Asay and Hayes [75A01]).

Along with, and closely connected to, the developments in precise impact techniques is the development of methods to carry out time-resolved materials response measurements of stress or particle velocity wave profiles. With time resolutions approaching 1 ns, these devices have enabled study of mechanical responses not possible in the early period of the 1960s. The improved time-resolutions have resulted from direct measurement of stress or particle velocity, rather than from improved accuracy and resolution in measurement of position and time. In a continuation of this trend, capabilities are being developed to provide direct measurements of the rate-of-change of stress. With the ability to measure such a derivative function, detailed study of new phenomena and improved resolution and accuracy in descriptions of known rate-dependent phenomena seem possible. 

Shock-compressed solids and shock-compression processes have been described in this book from a perspective of solid state physics and solid state chemistry. This viewpoint has been developed independently from the traditional emphasis on mechanical deformation as determined from measurements of shock and particle velocities, or from time-resolved wave profiles. The physical and chemical studies show that the mechanical descriptions provide an overly restrictive basis for identifying and quantifying shock processes in solids. These equations of state or strength investigations are certainly necessary to the description of shock-compressed matter, and are of great value, but they are not sufficient to develop a fundamental understanding of the processes. 

In the mechanism of an interfacial catalysis, the structure and reactivity of the interfacial complex is very important, as well as those of the ligand itself. Recently, a powerful technique to measure the dynamic property of the interfacial complex was developed time resolved total reflection fluorometry. This technique was applied for the detection of the interfacial complex of Eu(lII), which was formed at the evanescent region of the interface when bathophenanthroline sulfate (bps) was added to the Eu(lII) with 2-thenoyl-trifuluoroacetone (Htta) extraction system [11]. The experimental observation of the double component luminescence decay profile showed the presence of dinuclear complex at the interface as illustrated in Scheme 5. The lifetime (31 /as) of the dinuclear complex was much shorter than the lifetime (98 /as) for an aqua-Eu(III) ion which has nine co-ordinating water molecules, because of a charge transfer deactivation. 

Fig. 2.6.10 Specialized experimental set-up for microfluidic flow dispersion measurements. Fluid is supplied from the top, flows via a capillary through the microfluidic device to be profiled and exits at the bottom. The whole apparatus is inserted into the bore of a superconducting magnet. Spatial information is encoded by MRI techniques, using rf and imaging gradient coils that surround the microfluidic device. They are symbolized by the hollow cylinder in the figure. After the fluid has exited the device, it is led through a capillary to a microcoil, which is used to read the encoded information in a time-resolved manner. The flow rate is controlled by a laboratory-built flow controller at the outlet [59, 60].

Figure 28 TIC plot and the time-temperature resolved profiles of some molecular ions recorded obtained from the DPMS of PC. Reprinted with permission from Puglisi et al. [69]. Copyright 1999, American Chemical Society.

Fig. 4.8. Fluorescence lifetime of a stained section of Convallaria resolved with respect to lifetime, excitation and emission wavelength (A) intensity image integrated over the time-resolved excitation-emission matrix (EEM) (B, D) time-integrated EEM from areas A and B respectively in (A) (C) fluorescence decay profile for /ex 490 nm and Aem 700 nm corresponding to area A (E) fluorescence decay profile for Aex 460 nm and /em 570 nm corresponding to area B.

---