Acoustic plasmon mode

A number of methods are available for the characterization and examination of SAMs as well as for the observation of the reactions with the immobilized biomolecules. Only some of these methods are mentioned briefly here. These include surface plasmon resonance (SPR) [46], quartz crystal microbalance (QCM) [47,48], ellipsometry [12,49], contact angle measurement [50], infrared spectroscopy (FT-IR) [51,52], Raman spectroscopy [53], scanning tunneling microscopy (STM) [54], atomic force microscopy (AFM) [55,56], sum frequency spectroscopy. X-ray photoelectron spectroscopy (XPS) [57, 58], surface acoustic wave and acoustic plate mode devices, confocal imaging and optical microscopy, low-angle X-ray reflectometry, electrochemical methods [59] and Raster electron microscopy [60]. 

In summary, it is shown that the superconducting state of the novel family of layered superconductors, the metalochloronitrides, is provided by the plasmon mechanism, or more specifically, by the exchange of acoustic plasmons, the existence of which is specific to layered conductors. To the best of our knowledge, this is the first observed system with self-supported superconductivity, that is, with the pairing provided by collective modes of the same electrons as those undergoing the superconducting transition. 

A new experimental result is the observation of a broad and weak signal in the gap between the acoustic and optic branches and marked in fig. 23 with triangles. Such a mode has been observed before in IV chemically collapsed SmS by Mook et al. (1978). These modes are probably connected with bound heavy-electron plasmon-phonon modes where the f-like quasiparticles in the narrow bands below (described in section 4.1.1.2 and shown in figs. 2d and 14) couple to the phonons and perform collective oscillations. We recall that we have two plasrria oscillations, one for normal mass electrons and one for heavy mass electrons in the far infrared. It is the latter plasmon modes which are expected to couple to acoustic phonons in an out of phase motion as first proposed by Varma (1976). This idea has been quantitatively expanded in papers by Entel et al. (1979), Sinha and Varma (1983) and Stiisser et al. (1982). Further investigation of these modes seems necessary, however, they are only rarely observed (see also section 4.3.1.2). 

Direct binding systems. Many biosensors that utilize receptors as a mode of obtaining selectivity depend on the detection of the binding event, using devices such as surface plasmon resonance, surface acoustic waves, and fluorescence quenching [27]. 

To study the carrier and vibrational relaxation dynamics, mode-locked laser systems, which provide femtosecond pulses and fast and sensitive detection systems are necessary. For detection, streak cameras are used for measurements with time resolution in the subpicosecond range or CCD cameras for time-integrated measurements. For the latter, time resolution can be achieved by using optical Kerr gates or upconversion [266,268]. In general, the two mainly used optical detection mechanisms for coherent phonons (optical, acoustical, or LO-plasmon coupled modes) are the pump/probe [280-285] and the four-... 

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