Optical force model

We may suppose several motive forces arising from, for example, electro- and photostriction [Borrelli et al., 2002 Bonora et al., 2011), plasmon [polariton)-coupled motions [Dufftetal., 2009), and Coulombic repulsion [Shimakawa et al., 1998 Shimakawa, 2007). As described in the next section, the author proposes that the optical force, including light pressure and torque, is the most plausible, which can provide overall Interpretations on the deformations in the As-S[Se) system, except a-Se. Optical force models have also been adopted for interpreting photodeformations of polymer microgels [Juodkazis et al., 2000) and azo-polymer nanospheres [Barille et al, 2010). 

In short, the optical force model appears to provide overall explanations for all the deformations of semifree or flexible As2S(Se)3 samples. Nevertheless, we face, at least, two big problems. 

The sample behaves as a viscous fluid, for example, glycerol at 20°C. To overcome this big discrepancy, we may envisage some ideas— for example, resonant enhancement of optical forces [Truong and Shen, 2007], dependence of viscosity upon scales and shear rate [non-Newtonian flow], and/or some coupling [or positive feedback] between fluidity and optical force, which is internally generated in the glass, in contrast to the conventional photoinduced fluidity monitored under external forces. In addition, photoinduced fluidity may have some vector component that was not examined previously. Further studies are needed. 

In addition, the ultimate shape of the flake is also mysterious. Thick [ 4 pm] and thin [ 1 pm] AS2S3 flakes tend to become as screws [Tanaka, 2008] and spiral filaments [Fig. 3.13], respectively, for which gyration directions are difficult to experimentally determine. The gyration may be related to photoinduced gyrotropy [Lyubin and Klebanov, 2003], but its mechanism has been left unexplained [DiVincenzo, 1988]. The filamentation may be affected by Kerr self-focusing effects [Polynkin et al., 2011] under photoinduced fluidity. These speculations also remain to be studied. 

The simplest may be the one using intensity modulated patterns produced by two coherent beams. If the polarizations of the two 

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Several types of experiments have been carried out to investigate the stress state in the head of the bolt created by the body forces. The results of the finite element model experiment can be seen in Fig. 2, and those of the optical plane model experiment are presented in Fig. 3. 

As already noted, Newton replaced the concept of mechanical entanglement with the postulate of short-range interparticle forces of attraction and repulsion and applied this model in his Principia of 1687 to rationalize Boyle s law relating gas pressure and volume. However, it was not until the first decade of the 18th century that this new dynamic or force model was first specifically applied to chemical phenomena by the British chemists, John Freind and John Keill, and by Newton himself in the finalized version of the 31st query appended to the 1717 and later editions of his famous treatise on optics, where he succinctly summarized his new particulate program for chemistry ... 

Results will be split into various sections the first of which will be fundamentals of hot spots. This will include a summary of the most important developments in the theory of SERS hot spots for both the EM and CT enhancement mechanisms. The second section will cover developments in tip-enhanced Raman spectroscopy (TERS) which represents the idealized hot spot. Then some issues regarding hot spots and the single molecule will be tackled such as the magnitude of enhancement required for single-molecule detection, the effects of molecular orientation with respect to the hot spot as well as the possible influence of optical forces. Sections 4.4 and 4.5 will cover developments in the imaging and fabrication of SERS hot spots, respectively, which have important implications for theoretical modeling as well control of SERS hot spots. The chapter will conclude by summarizing some of the applications of SERS hot spots that have been recently reported. 

While the Lorentz model only allows for a restoring force that is linear in the displacement of an electron from its equilibrium position, the anliannonic oscillator model includes the more general case of a force that varies in a nonlinear fashion with displacement. This is relevant when tire displacement of the electron becomes significant under strong drivmg fields, the regime of nonlinear optics. Treating this problem in one dimension, we may write an appropriate classical equation of motion for the displacement, v, of the electron from equilibrium as... 

The above measurements all rely on force and displacement data to evaluate adhesion and mechanical properties. As mentioned in the introduction, a very useful piece of information to have about a nanoscale contact would be its area (or radius). Since the scale of the contacts is below the optical limit, the techniques available are somewhat limited. Electrical resistance has been used in early contact studies on clean metal surfaces [62], but is limited to conducting interfaces. Recently, Enachescu et al. [63] used conductance measurements to examine adhesion in an ideally hard contact (diamond vs. tungsten carbide). In the limit of contact size below the electronic mean free path, but above that of quantized conductance, the contact area scales linearly with contact conductance. They used these measurements to demonstrate that friction was proportional to contact area, and the area vs. load data were best-fit to a DMT model. 

Kolb and Franke have demonstrated how surface reconstruction phenomena can be studied in situ with the help of potential-induced surface states using electroreflectance (ER) spectroscopy.449,488,543,544 The optical properties of reconstructed and unreconstructed Au(100) have been found to be remarkably different. In recent model calculations it was shown that the accumulation of negative charges at a metal surface favors surface reconstruction because the increased sp-electron density at the surface gives rise to an increased compressive stress between surface atoms, forcing them into a densely packed structure.532... 

In the continuum and semicontinuum models of es, long-range forces due to distant solvent molecules are usually represented by the optical and static dielectric constants. In a true continuum model, the continuity is extended to the origin or to the surface of the cavity. In some sense, the continuum and semicontinuum models both contain both short- and long-ranged interactions. The main difference is that in the semicontinuum model, the molecules in the first shell(s) are structured. 

Fig. 2.2. Two generation models of coherent optical phonons, (a), (c), (e) impulsive stimulated Raman scattering (ISRS). (b), (d), (f) displacive excitation of coherent phonons (DECP). Graphs (e) and (f) display the time evolution of the driving force (grey areas) and that of the displacement (solid, curves) for ISRS and DECP, respectively...

Isotope superlattices of nonpolar semiconductors gave an insight on how the coherent optical phonon wavepackets are created [49]. High-order coherent confined optical phonons were observed in 70Ge/74Ge isotope superlattices. Comparison with the calculated spectrum based on a planar force-constant model and a bond polarizability approach indicated that the coherent phonon amplitudes are determined solely by the degree of the atomic displacement, and that only the Raman active odd-number-order modes are observable. 

In the present review, first we will describe how to fabricate artificial photosynthetic reaction center in nanometer scales by making use of phase separation in mixed monolayers of hydrocarbon (HC) and fluorocarbon (FC) amphiphiles [2,5,20-26] as shown in Fig. 2b [3]. The phase separated structures were studied by SPMs such as AFM, SSPM, and scanning near-field optical/atomic force microscopy (SNOAM) [27-33] as well as a conventional local surface analysis by SIMS [3,5], The model anionic and cationic HC amphiphilic... 

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