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Raman spectral bandwidths and bandshapes can provide detailed information on the physics and chemistry of a sample. The Raman band reported by a spectrometer (observed Raman band [ORB]) is a result of contributions from the true, intrinsic Raman band (IRB) and the spectrometer slit function. To obtain the IRB spectral width and shape, the effects of the spectrometer slit function must be removed from the ORB by measuring the spectrometer slit function and modeling the ORB as a convolution of the IRB and slit function. Though this model has proven to be useful, it is not based on physical parameters of the measurement and is limited. Thus, new ways to model Raman bandshape and bandwidth are needed. I previously developed a new method of modeling Raman bands using spectrometer geometric optics to examine the dependence of Raman band intensity on slit width. The model calculates the intensity of the ORB from the contributions of a continuum of dispersed slit functions. Here, I extend the use of this model for examining ORB spectral widths and shapes. I show that the model produces the same result as the convolution model when using Lorentzian Raman and Gaussian slit functions, confirming the validity of the model. However, in contrast to the convolution model, the new model is based on spectrometer geometric optics allowing one to account for various optical effects when modeling Raman spectra. This is demonstrated by modeling the effects of slit width on the Raman spectrum. I use the model to provide a detailed, physical understanding of the effects of slit width and IRB width on Raman bandshapes. [ABSTRACT FROM AUTHOR]

This paper reports the behavior of extraordinary optical transmission (EOT) through 1D plasmonic nanostructure devices when thickness and periodicity of silver film simulated on glass substrate are fixed and only slit width is varied. Transverse magnetic (TM) polarized photon incident normally at the grating structure and zero-order transmission spectra has been extracted. Fano-resonance associate with the excitation of the surface plasmon polaritons (SPPs) has been evaluated carefully to calculate EOT. Excited plasmons along with the Febry-Perot mode have contributed toward the EOT through the periodic slits in the grating device. It has been found that its numerical value of EOT is maximum at a particular slit width, i.e., 409 nm, which is greater than one half and less than two third of periodicity, when wavelength of light is comparable with periodicity. This unique behavior is associated with the maximum incident energy coupled to the excited plasmon due to fundamental plasmonic mode being the most efficient. Such optimal devices find many applications in real world, e.g., light-emitting diodes (LEDs), biosensing, and SERs. [ABSTRACT FROM AUTHOR]

The present work investigates the effect of geometrical parameters of 1D nanograting on surface plasmon resonance (SPR) and plasmonic bandgap (PBG). The use of plasmonic grating device in various electronic devices is based on correct value of bandgap energy. For this purpose, various nanograting structures having regular periodic ridges in 1D has been modeled in the form of a gold film on glass substrate using finite element analysis in RFRF Module of COMSOL (Multiphysics) 5.3a licensed version. In the designed structures, firstly, the periodicity of the grating varied while keeping the slit width and film thickness constant. Furthermore, the thickness of the grating also varied while the periodicity and slit width is kept constant and transmitted mode for each structure is studied to find the suitable value of film thickness for optimizing the device. At the end, the slit width varied while keeping the periodicity and film thickness constant. Due to increase in slit width, the bandgap energy increases until slit width equals to nearly half of periodicity after this bandgap energy decreases and associated with the sinusoidal behavior of the device which support fundamental plasmonic mode. The increase in film thickness results a linear increase in bandgap energy as long as the film thickness is comparable to the skin depth of gold and plasmonic bandgap energy is high for smaller values of periodicity and decreases with increasing periodicity. Due to the ability to control the optical properties, the PBG is expected to have a major impact on technology. [ABSTRACT FROM AUTHOR]

Effect of different gold (Au) grating structures on light absorption in solar cell is investigated by finite elemental analysis using COMSOL multiphysics-RF module. The geometry of the solar cell consists of a 50-nm Au film on the substrate of amorphous silicon (a-Si). An optimum value of the slit width (w) of the Au grating has been obtained whereas periodicity of the grating structure remained the same. The periodicity in the grating device was chosen in such a way that the excitation of the surface plasmon polritons (SPPs) lies in the IR or NIR region where most of the spectrometers work well in practical life. Far-field transmission spectra were extracted from the grating device when illuminating with p-polarized light through the substrate side. Near-field plots of the Fano resonance (dip) associated with the excitation of the surface plasmon polritons (SPPs) were carefully examined to understand the underlying physics. It was deduced from the results that a grating device with slit width of 250-350 nm is the most efficient which reveals the fact that such device offers intermediate scattering from the grating structure and supports fundamental plasmonic mode. Hence, such devices absorb more light being most efficiently and find application in solar cell. [ABSTRACT FROM AUTHOR]

The critical temperatures of bulk and confined atomic fluids are investigated using values of the vapour−liquid interfacial free energy of coexistence obtained from grand-canonical transition-matrix Monte Carlo simulations using a histogram reweighting technique. The temperature corresponding to zero interfacial free energy of coexistence is the estimated critical temperature for the system under investigation. Slit width of confined atomic fluid for this investigation is varied from 40 to 1 fluid particle diameter. The obtained critical temperatures have shown nonlinear monotonic trend with inverse of slit width. Moreover, five different linear regimes of critical temperature are observed in the studied range of slit width. Interestingly, in the slit width range of less than two fluid particle diameters, the critical temperature approaches two-dimensional value and remains approximately indifferent with a decrease in slit width up to one fluid particle diameter. This investigation also reveals that the critical temperature of bulk and confined atomic fluid estimated using the vapour−liquid interfacial free energy of coexistence is within reasonable accuracy with that obtained using the simplified form of scaling law. [ABSTRACT FROM PUBLISHER]

This research work reports the excitation of surface plasmon polaritons (SPPs) in a 1D grating device in a gold film on glass substrate. Various grating structures have been modelled using finite element analysis (FEA) in comsol RF module. The periodicity in such devices remains constant, whereas slit width is changed for each structure. We have studied the effects of slit width on SPP resonances and formation of the plasmonic bandgap. The trend shows that bandgap energy increases with increasing slit width and reaches a maximum value for slit width nearly equal to half of the periodicity in the grating structure and then decreases which is a new and important observation. The possible reason for this optimum value of the slit width corresponds to the absence of higher plasmonic modes and the sinusoidal nature of the slit. [ABSTRACT FROM AUTHOR]

Abstract: We present the numerical investigation of the optical transmission through a periodic gold nano-slit structure composed with two non-identical layers, and compare it with that of double-layer structure with two identical layers. The optical enhancement is attributed to the surface Plasmon resonance collaborated with the localized waveguide resonance. It is shown that the transmission behaviors are strongly dependent on the layer separation and lateral displacement between the two single metallic gratings. Especially, it is found that extraordinary transmission exists even if the slit of one layer shifts laterally over that of the other one to the situation that no light can propagate directly when layer separation D =0. When the slit widths of two layers are not equal, the surface plasmon resonance peak alternately decreases and increases twice, and the localized waveguide resonance peak appears at a longer wavelength as the lateral displacement varies for a non-zero layer separation, which differs from the situation with two identical layers. These transmission properties of the structures show promise for applications in optical devices. [ABSTRACT FROM AUTHOR]

During the dissolution of solid surfactants in water, various types of nonequilibrium microstructures have been observed. The most important one is the myelin growth which can be observed when some poorly water soluble surfactants such as phosphatidylcholine (PC), Aerosol-OT (AOT), etc. are contacted with water. In this study initial myelin growth for a period of 2–4 s is studied both qualitatively as well as quantitatively in all the directions with respect to water flow in a PC system using digital video microscopy. Further, overall myelin growth is studied by means of optical microscopy to understand the effect of distance between cover slip and glass slide on myelin growth. Experiments are also performed to study effect of additives (silica) to lamellar phase on diffusion coefficients. It has been observed that the presence of silica particles causes extensive coiling of myelin structures. The mechanism of water transport into the lamellar phase during myelin growth is investigated by using silica in a colloidal range as dopant material. [Copyright &y& Elsevier]

• RRF used in Potency Assay of drug products with multiple active compounds can vary drastically and make potency results inconsistent. • The settings of "slit", "step", "band width", and "data collection module" contribute significantly to this variation but rarely acknowledged. • The impacts of these factors to RRF and the interaction of the settings are thoroughly analyzed and discussed in this paper. • Practical considerations are given for the application of RRF methodology to potency assay for multiple APIs and impurity analysis. • Instrument settings and their impact to RF and RRF should be particularly evaluated during method development and also method transfer stage. Relative Response Factors (RRFs) can be used for quantitation of one compound against another and it is widely used for Impurity analysis of pharmaceutical products; however, the application in potency assay is limited. Through an extensive study shown in this paper, it can be concluded that using the "RRF methodology" for potency assay is much more challenging compared to impurity analysis, due to the much tighter criteria required for potency analysis. The effects of instrument settings, which are rarely discussed or recognized in current HPLC analytical method development and quality release testing, are discussed. These factors impact the RRF just as much as other commonly recognized HPLC parameters. The effects of UV detector settings, i.e. Slit Width, Step Width, Band Width, and Data Collection Module, have been explored. This phenomenon has been demonstrated using three compounds to observe the impact of their quantitation due to the significant RRF variations. Finally, principles to reduce RRF variations have been discussed, and practical considerations of RRF application to method development and method transfer are provided. [ABSTRACT FROM AUTHOR]

We demonstrate that the interference pattern of the plasmonic and photonic modes can be controlled by changing the slit width of a square slit structure. Based on the analyses of the plasmonic and photonic modes of slits with different widths, we theoretically derived the expressions of wavefield generated by a square slit. A far-field scattered imaging system is utilized to collect the intensity distribution experimentally. Various interference patterns, including stripes, square-like lattice array, and diamond-like lattice array, have been observed by adjusting the slit widths. In addition, the results were validated by performing finite-difference time-domain simulations, which are consistent with the theoretical and experimental results. [ABSTRACT FROM AUTHOR]