Showing 3 results for Absorption Cross Section
Mohammad Javad Azarm, Alireza Keshavarz, Gholamreza Honarasa,
Volume 15, Issue 1 (1-2021)
Abstract
The absorption cross-section of gold and silver nanoparticles has been demonstrated in confined wavelength spectra based on Mie's theory. For this purpose, the numerical study performed with COMSOL for defined particle size to clarify absorption spectra and final results have been compared with experimental data to express the absorption peak occurs in higher wavelength for large particle size which is in around 530 nanometers for gold and 400 nanometer for silver particles. These results show that particle size affects directly on absorption spectra of metallic nanoparticles.
Parisa Khajegi, Majid Rashidi-Huyeh,
Volume 15, Issue 1 (1-2021)
Abstract
Nobel metal nanoparticles (NPs) are widely used in various applications including optical and biological sensors, biomedicine, photocatalysts, electronics, and photovoltaic cells. The optical properties of gold NPs are surveyed in this paper under the Localized Surface Plasmon Resonance (LSPR) effect, which increases the light absorption and scattering at the LSPR wavelength. This LSPR frequency depends on various factors, including the shape and size of the particles as well as incident electromagnetic polarization. Here, the optical response of gold NPs with different shapes and sizes are investigated using the finite element method (FEM). The results show that the bandwidth, amplitude, and LSPR wavelength depend on the shape and dimensions of the NPs as well as the polarization of the incident light. The LSPR wavelength changes from 500 to 650 nm for different shapes of the gold NPs including sphere, octahedral, cube, ellipsoid, triangle, and with identical volume. To study the NP size effect on the optical properties, the absorption and scattering cross-sections (CSs) are also investigated for different sizes of NPs. The results show a redshift in the LSPR wavelength by increasing the NP size.
Mr Patrick Enenche, Dr Michael David, Dr Caroline Alenoghena, Mr Supreme Okoh,
Volume 15, Issue 2 (7-2021)
Abstract
The value of ozone absorption cross section (OACS) is a key parameter used in the configuration of gas sensors. Sadly, the variations of certain parameters among others such as temperature, pressure, and optical path-length in a given spectrum can affect the values of OACS. As a result, there have been several discrepancies in the value of OACS. Recently, the simultaneous effects of optical path-length were investigated in the visible spectrum. Hence, there is the need to also carry out the same investigation in the UV spectrum. So, in this paper, we have reported the combined variation effects of temperature (100 K–350 K), and optical path-length (0.75 cm–130 cm) on OACS in the UV spectrum. We used the method of optical absorption spectroscopy as deployed in a model software called Spectralcalc. The software comprising the HITRAN12 latest line list was used to simulate OACS values. Simulated results were obtained using the latest available line list on the HITRAN12 Spectralcalc simulator. Our obtained results were slightly different from those reported for the visible spectrum but followed a similar trend, in that it showed a decrease in the OACS with an increase in the temperature from 100 K to 350 K at 279.95 nm and 257.34 nm by 1.09 % and 1.43 % respectively. While optical path-length had zero effect on it. We, therefore, conclude that at constant pressure, OACS depends on both temperature and absorption wavelength but not on optical path-length. The analysis reported in this work only seeks to address the differences in the OACS relative to temperature in the UV spectrum. So, the results obtained in this paper can be used to optimally configure ozone gas sensors to obtain an accurate measurement.
