Phase-sensitive measurements

As with alternating electrical currents, phase-sensitive measurements are also possible with microwave radiation. The easiest method consists of measuring phase-shifted microwave signals via a lock-in technique by modulating the electrode potential. Such a technique, which measures the phase shift between the potential and the microwave signal, will give specific (e.g., kinetic) information on the system (see later discussion). However, it should not be taken as the equivalent of impedance measurements with microwaves. As in electrochemical impedance measurements,... 

As mentioned at the beginning of this chapter real phase-sensitive measurements of electrochemical systems have not yet been performed. Not only is the experimental technique difficult, but a reliable theory of... 

We hope that the studies summarized above will motivate time-resolved interference experiments on Jahn-Teller systems. Half-odd quantum numbers for molecular pseudorotation have been reported in the continuous wave spectra of Na, [47], benzene [48] and sym-triazine [44]. The half-odd quantum numbers are strong evidence for the presence of geometric phase factors. Benzene and sym-triazine have nondegenerate ground states and would therefore be the most obvious choices for phase sensitive measurements of the kind we propose. The 3s E Rydberg state of 5ym-triazine has the simplifying feature of exhibiting Jahn-Teller... 

Nevertheless, macrojunctions, e.g. between Pb and Y123, have been claimed to be successful, and are extensively used for some phase-sensitive measurements. It is also reported that good-quality planar junctions can be formed by atomic-layer epitaxial growth (Matsumoto et al. 1995). 

Knall et al. have tested a series of europium complexes with antenna chromo-phores in different polymer matrices in terms of sensitivity, response time, and dynamic range for the sensing of water vapor. A copolymer containing a Eu " chelate that can be spin-cast as thin film on glass slides was developed [110]. Scheme 6 shows the chemical structure of the polymerizable precursor 29. This complex can be copolymerized with norbomene-2,3-dicarboxylic acid dimethyl ester by means of ring opening metathesis polymerization. The sensor spots respond to water vapor by reversible luminescence quenching, which can be analyzed by means of phase sensitive measurements of luminescence lifetime [110]. 

In porous silicon (PS), a is dramatically decreased as suggested from thermal flow measurements (Drost et al. 1995). For characterizing the thermal parameter in nanostructures Uke PS, two major ways have been employed to generate a probing signal of the thermal fluctuation electrical input and noncontact optical incidence. The most useful method in the former case is so called the 3(0 method (Cahill 1990), in which the third-harmonic component of the alternating thermal oscillation with a certain frequency is selectively detected by a phase-sensitive measurement. 

Shen and Ostroverkhov performed phase-sensitive measurements of the air-water interface in a further developed experimental setup using a quartz reference plate and a phase modulator (Fig. In partic-... 

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