Probing techniques

B1.13.4.1 SMALL MOLECULES THE DUAL SPIN PROBE TECHNIQUE... 

B2.5.4.2 LASER FLASH PHOTOLYSIS AND PUMP-PROBE TECHNIQUES... 

Figure B2.5.8. Schematic representation of laser-flash photolysis using the pump-probe technique. The beam splitter BS splits the pulse coming from the laser into a pump and a probe pulse. The pump pulse initiates a reaction in the sample, while the probe beam is diverted by several mirrors M tluough a variable delay line.

Hasegawa M, Sugimura T, Shindo Y and Kitahara A 1996 Structure and properties of AOT reversed micelles as studied by the fluorescence probe technique Colloids Surf. A 109 305-18... 

The lubricant properties of alkanethiols and fluorinated alkanes have been studied extensively by scanning probe techniques [163]. In agreement with experiments on LB monolayers it was found that the fluorocarbon monolayers show considerably higher friction than the corresponding hydrocarbon monolayers [164, 165 and 166] even though the fluorocarbons are known to have the lowest surface free energy of all organic materials. 

L. J. Kricka, ed., Nonisotopic DNA Probe Techniques, Academic Press, Inc., San Diego, Calif., 1992. 

The small (<1 cm) sizes and brief (<1 //s) lifetimes of the fusion research plasmas preclude the use of most probe techniques. Laser pulse imaging... 

Figures 4c and 4d illustrate what happens when the incident electron probe is focused to illuminate alternately a crystallite in the center of the image (labelled twin) (Figure 4c) and another crystallite adjacent to the twin (Figure 4d). This focused-probe technique is sometimes referred to as micro-diffi-action. Two effects are evident in these micro-diffraction patterns. First, the diffraction patterns consist...

Additional suggested resources for the reader include introductory articles on scanning probe techniques for materials properties measurement [82,83J. A comprehensive manual describing various surface preparation techniques, experimental procedures and instrumentation is also a good resource [84J, although the more recent modulation based techniques are not covered. Key textbooks include Johnson s on contact mechanics [51J and Israelachvili s on surface forces [18J, as well as a treatment of JKR/DMT issues by Maugis [85J. 

In Fig.. I we present the temperature dependence of the conductance for one of the CNTs, measured by means of a three-probe technique, in respectively zero magnetic field, 7 T and 14 T. The zero-field results showed a logarithmic decrease of the conductance at higher temperature, followed by a saturation of the conductance at very low temperature. At zero magnetic field the saturation occurs at a critical temperature, = 0.2 K, which shifts to higher temperatures in the presence of a magnetic field. 

In many respects the time-resolved pump-probe technique is similar to the CW counterpart. The use of pulsed laser light permits direct probing of both the magnitude of the PA and its dynamics. The experimental arrangement is practically the same as for the CW version, i.e., both pump and probe beams are focused and overlapped onto same spot on a sample. In addition, the pump and probe pulses are synchronized so that the lime interval t between them is constant and confined to a certain time range (in our case up to 3 ns). 

In this section experimental results are described, which are obtained by applying the conventional pump-probe technique to m-LPPP films kept in vacuum at the temperature of liquid nitrogen [25], These results allow the identification of the primary excitations of m-LPPP and the main relaxation channels. In particular, the low and high excitation density regimes are investigated in order to get an insight into the physical processes associated with the emission line-narrowing phenomenon. 

Accordingly, the ionic conductivity in an electrolyte with negligible electronic conduction (/jon jtolal) may be determined by Ohm s law, provided that unpolarizable electrodes are employed. To overcome this limitation, separate voltage probes in the shape of identical electronic leads connected to the electrolyte at positions separated by a distance L may be employed (four-probe technique [38]). Under these... 

Proton inventory technique. 21.9-220 Pseudo-first-order kinetics, 16 Pulse-accelerated-flow method. 255 Pulse radiolysis, 266-268 Pump-probe technique. 266... 

The work function, , of a metal surface can be measured relatively easily and when using the Kelvin probe technique, in situ, i.e., during catalyst operation.54,55 Three techniques are the most commonly used54-58 ... 

All three techniques are quite straightforward to use. The Kelvin probe technique has the advantage that it does not require vacuum conditions, thus a catalyst can be studied under atmospheric or higher pressure. 

As also already shown in Figures 5.8 to 5.16 the validity of Eqs. (5.18) and (5.19) has been confirmed by several laboratories using the Kelvin probe technique, as well as UPS (via electron cutoff energy) and in a semiquanti-tative manner via the PEEM technique. Experiment has also clearly shown that the validity of these equations, which include only thermodynamic properties, does not depend on which, if any, electrode is grounded.31 The same is clearly tme for electrochemical promotion in general, as should be obvious to every electrochemist reader. 

The technique of photoemission electron spectroscopy (PEEM) is a particularly attractive and important one for spatially resolved work function measurements, as both the Kelvin probe technique and UPS are integral methods with very poor ( mm) spatial resolution. The PEEM technique, pioneered in the area of catalysis by Ertl,72-74 Block75 76 and Imbihl,28 has been used successfully to study catalytic oscillatory phenomena on noble metal surfaces.74,75... 

Equation (7.12) has been reported since 199031 by several groups31 39,40,42 45 and has been confirmed using both the Kelvin probe technique and UPS, as already discussed in Chapter 5. Only one group46 has reported significant deviations from it, but the SEMs in that work show massive blocking nonporous electrodes which apparently do not allow for ion spillover. 

By comparing Figure 11.9 and the characteristic Po2(Uwr) rate breaks of the inset of Fig. 11.9 one can assign to each support an equivalent potential Uwr value (Fig. 11.10). These values are plotted in Figure 11.11 vs the actual work function G>° measured via the Kelvin probe technique for the supports at po2-l atm and T=400°C. The measuring principle utilizing a Kelvin probe and the pinning of the Fermi levels of the support and of metal electrodes in contact with it has been discussed already in Chapter 7 in conjunction with the absolute potential scale of solid state electrochemistry.37... 

Figure 11.11. Correlation between the equivalent potentials of the supports defined in Figure 11.10 and of the work function or absolute potential of the supports measured via the Kelvin probe technique in po2 =1 atm at 400°C.22...

Kelvin probe technique and work function measurement, 138, 205, 340 experimental details, 340 two-probe arrangement, 340 Kinetics... 

Three scanning probe techniques are described in more detail below the scanning tunneling microscope, the atomic force microscope, and the friction force microscope. 

The colloid probe technique was first applied to the investigation of surfactant adsorption by Rutland and Senden [83]. They investigated the effect of a nonionic surfactant petakis(oxyethylene) dodecyl ether at various concentrations for a silica-silica system. In the absence of surfactant they observed a repulsive interaction at small separation, which inhibited adhesive contact. For a concentration of 2 X 10 M they found a normalized adhesive force of 19 mN/m, which is small compared to similar measurements with SEA and is probably caused by sufactant adsorption s disrupting the hydration force. The adhesive force decreased with time, suggesting that the hydrophobic attraction was being screened by further surfactant adsorption. Thus the authors concluded that adsorption occurs through... 

The surface sensitivity of most electron probe techniques is due to the fact that the penetration depth of electrons into metals falls to a minimum of 4 to 20 A when their kinetic energy is between 10 and 500 eV. It is also convenient that electrons at these energies have de Broglie wavelengths on the order of angstroms. With a monochromatic beam, it is possible to do LEED. 

E. W. Van Stryland, M. Sheik-Bahae, in R. A. Lessard, H. Franke (eds.) Materials Characterization and Optical Probe Techniques, Vol. CR96, SPIE, Bellingham 1997. 

Stimming U, Vogel R. 1998. In-situ local probe techniques at electrochemical interfaces. In Lorenz WJ, Plieth W, eds. Electrochemical Nanotechnology. Weinheim Wiley-VCH. 

In order to relate material properties with plasma properties, several plasma diagnostic techniques are used. The main techniques for the characterization of silane-hydrogen deposition plasmas are optical spectroscopy, electrostatic probes, mass spectrometry, and ellipsometry [117, 286]. Optical emission spectroscopy (OES) is a noninvasive technique and has been developed for identification of Si, SiH, Si+, and species in the plasma. Active spectroscopy, such as laser induced fluorescence (LIF), also allows for the detection of radicals in the plasma. Mass spectrometry enables the study of ion and radical chemistry in the discharge, either ex situ or in situ. The Langmuir probe technique is simple and very suitable for measuring plasma characteristics in nonreactive plasmas. In case of silane plasma it can be used, but it is difficult. Ellipsometry is used to follow the deposition process in situ. 

Falk, J. L., Zhang, J., Chen, R., and Lau, C. E., A schedule induction probe technique for evaluating abuse potential Comparison of ethanol, nicotine and caffeine, and caffeine-midazolam interaction. Special Issue Behavioural pharmacology of alcohol. Behavioural Pharmacology 5(4-5), 513-520, 1994. 

Atom probe techniques have been used to investigate adsorption processes and surface reactions on metals. The FIM specimen is first cleaned by the application of a high-voltage field evaporation pulse, and then exposed to the gas of interest. The progress of adsorption and surface reaction is monitored by the application of a second high-voltage desorption pulse and a controlled time delay. 

Schraub, F. A., 1968, Isokinetic Sampling Probe Technique Applied to Two-Phase Flow, ASME 67-WA/FE-28, Annual Meeting, ASME, New York. (3)... 

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