Deconvolution of continuous internal bremsstrahlung spectra of 32P, 85Kr and 143Pr

An efficient method of deconvolution of the internal bremsstrahlung (IB) spectra accompanying the β‐decay in ³²P, ⁸⁵Kr and ¹⁴³Pr is presented. Experimental data is taken from the literature. The usual experimental values are folded with the response matrix of the detector system, and the Gold iteration technique is employed to deconvolve the detector response function for the continuous IB photon spectra. The response function of the detector is calculated using the peak to total ratio and the energy resolution of the detector. The results of the deconvolved IB spectra along with the theoretical calculations are presented. Copyright © 2007 John Wiley & Sons, Ltd.     

Deconvolution in X-ray photoelectron spectroscopy

Published Mg and Al Kα X-ray lineshapes have been used to study the removal of the effects of X-ray broadening in XPS spectra by deconvolution. These results are compared with spectra obtained for the same specimens in the same instrument using a monochromatic X-ray source. The use of deconvolution to remove analyzer broadening from spectra has also been examined, and it has been verified experimentally that the maximum improvement in the full width at half-maximum of a peak that can be achieved is 30%. Deconvolution has also been examined as a means to remove backgrounds from XPS spectra over wide energy ranges, up to 100 eV.     

Deconvolution of very low primary energy SIMS depth profiles

In this paper, the deconvolution of SIMS profiles analysed at very low primary energy (0.5 keV/O₂⁺) is addressed. The depth resolution function (DRF) of the SIMS analysis in presence of roughness is established and a deconvolution procedure is implemented without or in presence of roughness on samples containing delta-doped layers of boron in silicon. It is shown that the deconvolution procedure can lead to a great improvement of the full width at half maximum (FWHM) of the measured peaks in the case where no roughness in detected in the crater bottom. In the case where it is present, the conditions required to use a deconvolution procedure are discussed, and the deconvolution is implemented using precise and restrictive assumptions.     

Monochromator versus deconvolution for XPS studies using a kratos ES300 system

Deconvolution has been used by several workers to reduce or eliminate X-ray and analyzer-induced broadenings of XPS spectra, but there is a 30% limit on the amount of improvement in the FWHM of XPS peaks. Deconvolution algorithms generally used also increase the noise in the spectrum. Monochromatic X-ray sources can give high resolution data directly, but the count rates are generally low. Given these limitations, a comparison has been made to see which method of high resolution data acquisition. can achieve data of a certain quality in the least amount of time, for a given system, namely a Kratos ES300 photoelectron spectrometer. Signal-to-noise ratios are used as a means of comparing spectral quality at a given resolution. Results for the Kratos ES300 show that if the desired resolution could be achieved without deconvolution, an order of magnitude less counting time was needed for the Mg Kα standard source. If deconvolution is necessary, the counting times for both sources to achieve a given S/N ratio were found to depend mainly upon the signal-to-background ratios of the peak measured with each source. These results are illustrated for the S 2p doublet from MoS₂ and the Ni 2p peaks from oxidized stainless steel.     

Globally optimal superconducting magnets part I: minimum stored energy (MSE) current density map

Accurate determination of ¹H NMR signal intensities is useful for quantitative analysis of the hydrogen content and also to determine the relative peak intensity ratios in different application scenarios. To this end we have investigated the reliability and sources of intensity errors in ¹H solid-state MAS NMR. If sufficient resolution can be achieved by very high spinning speeds and high magnetic fields, quantification is straight forward. However, for poorly resolved spectra we show that small phase errors add a considerable amount of uncertainty. An analytical expression for the phase induced intensity-errors allowed us to suggest a robust and reliable recipe which is based on a combination of the spin-echo experiment, an extrapolation technique and a deconvolution algorithm which includes fitting of the signal phase. It significantly reduces errors caused by phase distortions, homonuclear dipolar dephasing, the receiver dead time delay and baseline rolling. The method was validated experimentally on samples with strong homonuclear dipolar interactions.     

The resolution obtainable in X-ray photoelectron spectroscopy with unmonochromatized Mg Kα radiation

The resolution obtainable in photoelectron spectra excited with unmonochromatized Mg Kα radiation is discussed and the various contributions to the instrumental resolution function considered; theoretical estimates are given. Experimental results are compared with theory. It is found that the instrumental resolution is 0.64 eV for a pass energy of 50 eV, with a lower limit of 0.57 ± 0.03 eV owing to the width of the exciting Mg Kα_1,2 radiation. However, the measured resolution is not much less than the values quoted for monochromator-equipped spectrometers.     

Fourier-ratio deconvolution and its Bayesian equivalent

We discuss how an inner-shell electron energy-loss spectrum can be processed using Bayesian (maximum-entropy or maximum-likelihood) deconvolution to simultaneously remove plural scattering and improve the energy resolution. As in Fourier-ratio deconvolution, a low-loss spectrum (recorded from the same area of specimen) is used as a kernel or resolution function. This procedure avoids the need to record the zero-loss peak in the absence of a specimen and uncertainties related to the width of the zero-loss peak. Unlike the case of Fourier-ratio deconvolution, we find that core-loss data do not require pre-edge background subtraction and extrapolation towards zero intensity; simply matching the intensity at both ends of the region is usually sufficient to avoid oscillatory artifacts. Using the low-loss spectrum as both data and kernel yields a zero-loss peak whose width provides an indication of the energy resolution as a function of the number of iterations. Finally, we argue that Fourier-ratio deconvolution or its Bayesian equivalent is the correct way to remove the substrate or matrix contribution to an energy-loss spectrum recorded from a particle on a substrate or embedded in a matrix.     

On the He(I) and Ne(I) photoelectron spectra of OCS

The He(I) (58.43 nm) and Ne(I) (73.59–74.37 nm) photoelectron spectra of carbonyl sulphide have been reinvestigated at an improved resolution and a high signal-to-noise ratio; deconvolution of the data was carried out to aid interpretation of the spectra. Improved values are deduced for the vibrational wavenumbers and the ionization energies. The spin—orbit components of the Ã²Π II level are well resolved and a value of 135 cm^?1 (17 ± 5 meV) is proposed for the splitting. Perturbations in the relative intensities are observed in the Ne(I) spectrum; they suggest that the autoionizing Rydberg state located around 73.7 nm is excited by the 73.59 nm Ne(I) line and contributes to populate, with different probabilities, the ionic levels of lower energy, and particularly the X?²Π state.     

测量分子荧光寿命的一种新方法

分子的荧光寿命,通常可用脉冲荧光法进行测量。若荧光寿命接近或小于仪器响应时间时,则观测到的荧光衰变曲线是真实的荧光衰变曲线与仪器响应函数卷积的结果。为此须采用解卷积方法来求得荧光寿命。解卷积运算不仅其计算过程繁重,而且计算结果受检测仪器响应函数的准确度的影响很大。 本工作提出一种新的测量荧光寿命的方法。该方法是根据观测的荧光衰变曲线的峰值所对应的时间tmax随荧光寿命的增大而单调地变大的关系,选用一些已知寿命的荧光物质作为标准样品,测量标准样品的tmax～τ关系曲线,然后测量待测样品的tmax,据此求出荧光寿命τ。这种方法简便、准确可毋须进行解卷积运算。     

Messung der Energieverlustspektren von Aluminium- und Silberfolien mit hoher Auflösung

The energy loss spectra of polycrystalline aluminium and silver foils have been measured with high resolution. For the plasmon energy of aluminium 14.97 eV is obtained. The half width of the plasmon peak is 0.60 eV corresponding to a relaxation time τ=1.1×10^?15 sec in fair agreement with optical data. In silver films of certain thicknesses the surface plasmon peak and the plasmon peak can be separated in the energy loss spectrum. The values of the energy losses are 3.64 and 3.78 eV respectively.     

On line shape of electromagnetically induced transparency in a multilevel system

We present a detail analysis of the line shape of electromagnetically induced transparency (EIT) in a Doppler broadened five level atomic system based on density matrix formalism. It has been shown that the velocity averaged EIT line shape in a multilevel system is very sharp. The effect of the ground state decay rates on the EIT peak has also been investigated. The linear and non-linear variations of the EIT line width (FWHM) for different pump and probe power ratios are shown. Considering the D₂ transition of ⁸⁵Rb atom the dependence of EIT width and height on pump power has been experimentally measured. Simulated spectra are compared with the experimentally obtained one. The effect of buffer gas on the EIT peak has also been observed experimentally as well as theoretically.     

EPR studies of15N- and2H-substituted pH-sensitive spin probes of imidazoline and imidazolidine types

The isotopically substituted analogs of pH-sensitive imidazoline and imidazolidine radicals have been synthesized and investigated with electron paramagnetic resonance (EPR) spectroscopy. The introduction of²H and¹⁵N into the structure of the radical is a useful approach to enhance the information obtained from spin-labeling experiments. The spectra of the radicals have been analyzed with 9.8 (X-band) and 130 GHz (D-band) EPR spectroscopy. The substitution of¹H for²H leads to significant narrowing of Gaussian line width, while the substitution of¹⁴N for¹⁵N in the nitroxyl fragment decreases both the number of spectral lines and Lorentzian line width. These effects result in a significant increase in the peak intensities up to 5–7 times for X-band EPR spectra of one of the imidazoline radicals (R4). The increase in spectral resolution allowed us to reveal the hyperfine interaction splitting with the attached proton (0.36 G) in the protonated form of the radical R4. The influence of proton exchange of the radicals with phosphate and acetate buffers on their EPR spectra has been studied in H₂O and D₂O. The corresponding rate constants of the proton exchange have been calculated from fitting of the simulated EPR spectra line shapes to experimental spectra. The data obtained demonstrated the advantages of the isotopically substituted spin pH probes in spectral resolution and sensitivity which can be an important factor particularly for applications in vivo where the fundamental sensitivity is much lower. The sensitivity of EPR spectra of these spin probes to the buffer capacity could be of practical importance taking into account the biological relevance of monitoring this parameter in some pathological states.     

基于光梳的腔增强傅里叶变换光谱：在碰撞线形研究中的应用

本文在近红外区域构造了基于光学频率梳的腔增强傅里叶变换光谱仪，并用于Ar干扰的CO振转跃迁的谱线研究，高灵敏度的测量波数从6270 cm^-1到6410 cm^-1，涵盖CO第二泛频带的P和R分支. 该光谱仪提供的高分辨率超过了由干涉图长度确定的傅立叶变换分辨率极限，成功消除了线型函数的振铃和展宽效应. 本文可观察到Voigt线型曲线外的碰撞效应. 通过拟合速度依赖的Voigt曲线重新得到碰撞线型曲线参数，并与使用基于光学频率梳的高精密连续激光光腔衰荡光谱测量结果非常吻合.     

Raman labeled nanoparticles: characterization of variability and improved method for unmixing

Raman spectroscopy can differentiate the spectral fingerprints of many molecules, resulting in potentially high multiplexing capabilities of Raman‐tagged nanoparticles. However, an accurate quantitative unmixing of Raman spectra is challenging because of potential overlaps between Raman peaks from each molecule, as well as slight variations in the location, height, and width of very narrow peaks. If not accounted for properly, even minor fluctuations in the spectra may produce significant error that will ultimately result in poor unmixing accuracy. The objective of our study was to develop and validate a mathematical model of the Raman spectra of nanoparticles to unmix the contributions from each nanoparticle allowing simultaneous quantitation of several nanoparticle concentrations during sample characterization. We developed and evaluated an algorithm for quantitative unmixing of the spectra called narrow peak spectral algorithm (NPSA). Using NPSA, we were able to successfully unmix Raman spectra of up to seven Raman nanoparticles after correcting for spectral variations of 30% intensity and shifts in peak locations of up to 10 cm⁻¹, which is equivalent to 50% of the full width at half maximum (FWHM). We compared the performance of NPSA to the conventional least squares (LS) analysis. Error in the NPSA is approximately 50% lower than in the LS. The error in estimating the relative contributions of each nanoparticle with the use of the NPSA are in the range of 10–16% for equal ratios and 13–19% for unequal ratios for the unmixing of seven composite organic–inorganic nanoparticles (COINs); whereas, the errors from using the traditional LS approach were in the range of 25–38% for equal ratios and 45–68% for unequal ratios. Here, we report for the first time the quantitative unmixing of seven nanoparticles with a maximum root mean square of the percentage error (RMS%) error of less than 20%. Copyright © 2012 John Wiley & Sons, Ltd.     

Response function of the CdZnTe SPEAR detector

The response function of the SPEAR CdZnTe detector developed by eV Microelectronics was studied in detail. This compact detector includes a CdZnTe crystal and a preamplifier. It is operational at room temperature. The energy range of the detector is between 10 keV and 1 MeV, and its relative resolution is less than 4% at 122 keV. The goal of our study was to establish an empirical analytical approximation of the response function to be used in Monte Carlo simulations (e.g. for spectrum unfolding). Various radionuclides were used for the study. The energy spectrum obtained from the detector not only showed smooth peaks but also had a tail on the low‐energy side of the peak. This tail part was more prominent at higher energies. By using the experimental spectrum for various nuclides such as ²⁴¹Am, ¹⁰⁹Cd, ⁵⁷Co and ¹³⁷Cs, the parameters required to replicate the experimental response with a peak plus exponential model were evaluated. Copyright © 2011 John Wiley & Sons, Ltd.     

Electroconductivity profiles in dense high explosives

A method for measuring the electroconductivity profiles behind the detonation front in dense solid high explosives with a resolution of 0.1 mm was developed. The method has a measurement range more than an order of magnitude wider than the available methods. During the detonation of pressed PETN, RDX, and HMX, an electroconductivity peak with an amplitude of several Ω^?1 cm^?1 and a width of 40 to 70 ns was observed. The peak width is in agreement with the available data on the width of the chemical reaction zone. The peak is accompanied by a tail with an electroconductivity several times lower.     

Quasi-particle excitations and phonon broadening effects in the O ls spectra of Ln(OH)3 (Ln = La,Nd, Sm and Gd)

The O ls photoelectron spectra of Ln(OH)₃ (Ln = La, Nd, Sm and Gd) can be approximated by the convolution of a core hole spectral density function and a response function which is related to the phonon broadening and instrumental broadening effects. A non-linear least-squares analysis on the convolution integral indicates that the lifetime of the O ls (in the energy domain) is strongly broadened by the phonon excitations. The FWHM (full width at half maximum) of the phonon excitations range from 1.3 to 2.6 eV.     

红外扫描和频振动光谱系统的激光线宽与光谱分辨率

本文报道了一个简化的利用可见光和红外光带宽来计算和频光谱分辨率的公式. 公式显示和频振动光谱的Voigt线宽可以通过振动模式的均匀线宽(洛伦兹线宽)、非均匀线宽(高斯线宽)、红外光与可见光的高斯线宽计算获得. 利用本实验室新搭建的频率分辨及偏振分辨的皮秒和频光谱系统验证了该公式的准确性. 实验结果显示,本激光系统获取的红外光的高斯线宽为1.5 cm^-1. 本激光系统的光谱分辨率约为4.6 cm^-1,结果与胆固醇单层膜光谱获取的光谱分辨率(3.5~5 cm^-1)基本一致.     

Bestimmung der Empfindlichkeit bei Tc-99-NMR-Messungen an einem 250-MHz-Spektrometer

By means of different concentrations the signal-to-noise ratios of Tc-99-NMR spectra were determined applying well measurable Tc-samples [tetrabutylammoniwn pertechnetate, TBA (TcO₄)J and a 250 MHz-spectrometer. The signal-to-noise ratios of the spectra were determined by using the integrated routines of the firm's software and accumulating different number of scans. By fittings of data of the signal-to-noise ratio dependence and by extrapolation the minimum Tc-concentralion could be empirically found out. Applying a duration of measurements of 12 hours about 10^?7 molar concentrations can be determined.