Metal photoacoustic detection

Photoacoustic Detection of Natural Circular Dichroism in Crystalline Transition Metal Complexes... 

Resonant photoacoustic gas spectrometry was adapted to fiber optic sensor technology32 as early as in 1984. A Mach-Zehnder arrangement was combined with a resonant photoacoustic cell for gap analysis. The pollutant gas NO2 was detectable in a concentration of 0.5 ppm. In a smart optical fiber hydrogen sensor, the fiber is coated with palladium metal which expands on exposure to hydrogen. This changes the effective optical path length of the fiber, which is detected by interferometry33. 

Figure 13 shows the calibration curve of phase-lag for the nickel foils of various thickness. This result suggests the possibility of estimating the thickness of plated materials on the metal. Figure 14 shows the PAXAS spectrum of nickel-plated copper. In the photoacoustic amplitude spectrum, EXAFS of copper at the subsurface of sample was still detected clearly. This means that PAXAS method can be applied... 

Instrumentation. Metal sheets are used as working electrodes. Piezoelectric elements were coupled mechanicaUy with this electrode by using a thin layer of grease [919-921]. Figure 5.145 shows the experimental setup. For increased sensitivity, the incident light beam was modulated by means of a mechanical chopper and the photoacoustic signal was detected via a lock-in ampUfier. 

There are some less widely studied types of inorganic photochemical systems. There is the phenomenon of photochromism, in which a system is driven one way by light and returns either thermally or photochemically. An example for us was the family of transition metal dithizonate complexes [51]. Photochemistry and calorimetry may be combined in photocalorimetry, to obtain enthalpies of reactions which are not clean or are not obtainable at all thermally [52], Similar information can be obtained from the photoacoustic effect [53]. Another interesting phenomenon is that of chemiluminescence, that is, the chemical production of an excited state reaction product, and the related process of electrogenerated chemiluminescence. This type of emission can be detected even when... 

When a nonradiative SP decays it generates heat at the metal/dielectric interface. This observation can be fruitfully exploited to detect the presence of SPs. In a photoacoustic approach, the prism/metal assembly is placed in an airtight chamber. SPs are excited with an intensity-modulated light beam the resulting periodic heat flow from metal to dielectric as a result of plasmon decay causes a periodic pressure variation in the dielectric which can be detected by a microphone in the sample chamber. A significant difference as compared with optical detection is that SPR is now detected as a maximum in response. This method is mainly used in fundamental studies where one is interested in SP decay. The method is less suited in situations where the dielectric of interest consists of a fluid, such as water. 

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