- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Spectroscopic and luminescence properties of Ho3+ ions doped Barium Lead Alumino Fluoro Borate glasses for green laser applications
摘要： Optically transparent Barium Lead Alumino Fluoro Borate (BaPbAlFB) glasses doped with different concentrations of Ho3+ ions were prepared by using melt quench technique. Raman spectral studies were conducted to understand the structural groups present in the as prepared glasses at room temperature. Spectroscopic investigations such as optical absorption, excitation, emission and decay measurements were conducted to understand the visible photoluminescence (PL) and lasing potentialities of BaPbAlFB glasses. The bonding parameters (δ) estimated from the absorption spectral features were used to understand the nature of bonding between Ho3+ ions and the surrounding ligands. The Urbach energy values estimated from the absorption spectral data are used to verify the amorphous nature of the present glass system. The Judd-Ofelt (J-O) theory has been applied to the measured oscillator strengths of the absorption spectral features to estimate the best fit J-O parameters (?λ, λ= 2, 4, and 6) useful in evaluating various radiative parameters for the prominent fluorescent levels of Ho3+ ions in BaPbAlFB glasses. The experimental lifetimes (τexp) are found to be decreasing with increase in Ho3+ ion concentration owing to energy transfer. The quantum efficiency (η) of Ho3+ ions doped BaPbAlFB glasses were estimated by correlating the experimental lifetimes (τexp) with the radiative lifetimes (τR). The strong visible emission, large stimulated emission cross-section (σse), high branching ratio (βR) and relatively good quantum efficiency (η) obtained for 5S2→ 5I8 (green) transition of 1mol% of Ho3+ ions doped BaPbAlFB glass reveals its suitability in designing and developing visible green lasers.
关键词： emission cross-sections,Holmium,glasses,quantum efficiency,CIE coordinates,photoluminescence
更新于2025-09-19 17:13:59
-
Nuclear Astrophysics with Lasers
摘要： A systematic program of investigations of nuclear reactions in laser-produced plasmas is addressed. Such reactions provide an important diagnostic tool for probing the dynamics and thermodynamics in the plasma and understanding laser ion acceleration and neutron production mechanisms. The goal will be to reach the level of knowledge that allows the measurement of fundamental nuclear cross-sections at low and high particle densities. The quantitative measurement of fusion probabilities in hot and dense plasmas will contribute significantly to our comprehension of stellar composition and evolution and will provide important information for development of fusion energy production and applications such as medical isotope production and compact neutron source development. All of these are some of the main goals of the European Extreme Light Infrastructure (ELI), the Shanghai Superintense Ultrafast Laser Facility, and the Station of Extreme Light in China and similar projects in other countries.
关键词： Fusion Reactions,Nuclear Astrophysics,Lasers,Cross-sections,Plasma
更新于2025-09-16 10:30:52
-
Efficient two-color two-step laser ionization schemes of λ <sub/>1</sub> ～ 250 nm and λ <sub/>2</sub> = 307.9 nm for heavy refractory elements—Measurements of ionization cross-sections and hyperfine spectra of tantalum and tungsten
摘要： We demonstrated efficient two-color two-step laser ionization schemes in the combined use of λ1 ～ 250 nm and λ2 = 307.9 nm, which are applicable to heavy refractory elements with an atomic number in the wide range of Z = 69–78. We investigated newly observed ionization schemes of tantalum and tungsten atoms in an argon-gas-cell-based laser ion source for the efficient ionization of atoms of unstable nuclei through the two-color two-step laser resonance ionization technique. We experimentally determined the ionization cross sections from the measured saturation curves by solving the rate equations for the ground, intermediate, and ionization continuum populations. Hyperfine structures of these elements were also studied to deduce the isotope-shift, pressure-shift, and pressure-broadening in the resonance spectra of the excitation transitions in the argon gas cell. The electronic factor F255 of the excitation transition λ1 = 255.2115 nm between the ground and intermediate states was deduced from the measured isotope shifts of stable 182,183,184,186W isotopes. The ionization schemes investigated here are applicable to extract any isotopes of these elements by considering the measured pressure shift and nuclear isotope shift in optimizing the wavelength λ1.
关键词： ionization cross-sections,laser ionization,tantalum,hyperfine spectra,tungsten
更新于2025-09-11 14:15:04
-
[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Comparisons Between Simulated and Measured X-band Signatures of Quad-, Hexa- and Octocopters
摘要： This paper presents and compares finite element method (FEM) and method of moments (MoM) monostatic radar cross-section (RCS) simulation results for an example quadcopter, hexacopter and octocopter at X-band, as well as comparing the simulations against measurements for quad- and hexacopters. In particular we explore the extent to which simplified CAD models can be used to estimate the scattering from multi-rotor unmanned aerial vehicles (UAVs). We also consider the importance of model complexity for micro-Doppler rotor simulations.
关键词： Doppler radar,radar cross-sections,Radar
更新于2025-09-11 14:15:04
-
[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Simulation of Near Field RCS to Reproduce Measurement Condition
摘要： Different approaches are presented to simulate the near field Radar Cross Section (RCS) of a perfectly conducting electrically large object. This type of environment is usually found in measurements at large anechoic chambers where the far field condition cannot be achieved, making it impossible to approximate the incident field by a planewave. Each approach will be implemented with Physical Optics (PO) for extremely large targets and an accelerated version of the Method of Moments for moderately large objects. The fast MoM method are either the Multilevel Adaptive Cross Approximation (MLACA) for an iterative solution or the Multiscale Compressed Block Decomposition (MSCBD) for a direct solution. This development and the performed simulations have been done with CAPITOLE-RCS commercial software developed by NEXIO.
关键词： physical optics,method of moments,radar cross-sections,inverse synthetic aperture radar,Numerical simulation,anechoic chambers
更新于2025-09-10 09:29:36
-
Encyclopedia of Spectroscopy and Spectrometry || Ion Collision, Theory ☆
摘要： Collisions between an ion and neutral species result in a number of possible outcomes depending upon the chemical and physical properties of the two reactants, their relative velocities, and the impact parameter of their trajectories. These include elastic and inelastic scattering of the colliding particles, charge transfer (including dissociative charge transfer), atom abstraction, complex formation and dissociation of the colliding ion. Each of these reactions may be characterized in terms of their energy-dependent rate coefficients, cross sections and reaction kinetics. This article outlines a theoretical framework for discussing these processes that emphasizes simple models and classical mechanics. The discussion of collision processes has been divided into two categories: low-energy and high-energy thermal or quasi-thermal collisions. Experiments under conditions – swarms, drift tubes, chemical ionization and ion cyclotron resonance – are strongly influenced by long-range forces and often involve ‘capture collisions’ in which atom exchange and extensive energy exchange are common characteristics. High-energy collisions are typically impulsive, involve short-range intermolecular forces and are direct, fast processes.
关键词： Low-energy Collisions,Elastic and Inelastic Scattering,Reaction Kinetics,Theory,Complex Formation,Rate Coefficients,Charge Transfer,Atom Abstraction,High-energy Collisions,Ion Collision,Dissociation,Cross Sections
更新于2025-09-04 15:30:14
-
Collisional - radiative model of xenon plasma with calculated electron impact fine-structure excitation cross sections
摘要： Detailed electron impact excitation cross section results for xenon in the wide range of incident energy from threshold to 1000eV are calculated using relativistic distorted wave (RDW) theory. Various transitions from the ground 5p6 state to the excited 5p56s, 5p56p, 5p55d, 5p57s and 5p57p as well as among these excited states are considered. The relativistic Dirac-Fock multi-configuration wave functions for the ground and excited states of the xenon are obtained and used in the calculations. Where available our cross section results are compared with previously reported measurements and calculations. We have also fitted the calculated cross sections through analytical formulae for plasma modeling purposes. As an application, using the obtained cross sections, a collisional Radiative (C-R) model coupled with an optical emission measurement from the inductively coupled Xe plasma is developed and the extracted plasma parameters are reported.
关键词： relativistic distorted wave theory,Electron impact excitation,cross-sections,collisional radiative model
更新于2025-09-04 15:30:14
-
AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Following electron impact excitation of single(58Ce, 59Pr, 60Nd, 61Pm, 62Sm, 63Eu, 64Gd, 65Tb, 66Dy, 67Ho) atom M subhell ionization cross sections by using Lotz’s equations
摘要： M shell and M subshells ionization cross sections(σM) and σMi(i = 1,.,5) following electron impact on single(Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho)atoms calculated. By using Lotz's equation in Matlab σMand σMi cross section values obtained for 12 electron impact energies Eoi in EMi≤Eo<5EMi range for each atom. Lotz’s parameters and special commands used for each σMi calculations. Starting allmost from Eo = EMi values; σMi and σMi are increasing rapidly with Eo. For a fixed Eo ≈ 3.5EMi while Z value increases from 58≤Z≤67 σM and σMi decrease with Z. Results show that for Eovalues close to EMi values, characteristic x-ray yields formation of Mi(i = 1,.,5) subshells decreases while competing other events (Auger electrons, Coster-Kronig transitions) are increase. These results will also help to understand some results which obtained from other electron-atom impact studies on σMi subshells.
关键词： Electron impact on single atom,Near Mi subshells threshold energy region.,Mi subshells ionization cross sections of single Ce to Tb
更新于2025-09-04 15:30:14
-
[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - A Complex Low-RCS Antenna System for the Placement of mm-Wave Automotive Radars behind Car Bumpers
摘要： Automotive radars are one of the key sensor technologies to develop reliable fully-automated cars. They are usually installed behind the bumper of the vehicle and therefore, multiple reflections can occur. The multiple reflections can be mitigated with the use of low-RCS (radar cross-section) antenna arrays. This paper presents the design of a complex low-RCS multiple antenna system that mimics a typical MIMO (multiple-input multiple-output) configuration. A prototype has been developed and tested. Approximately 17 dB of RCS reduction has been experimentally achieved. The measurement results show that the use of such a low-RCS antenna system can successfully reduce the amplitude of multiple reflections.
关键词： radar antennas,microstrip antenna arrays,millimeter wave radar,radar cross-sections
更新于2025-09-04 15:30:14