Changes In Spectrum Shape Research Articles

Fast Scanning Nitrogen-Vacancy Magnetometry by Spectrum Demodulation

We demonstrate a spectrum demodulation technique allowing for rapid imaging in scanning nitrogen-vacancy center magnetometry. Our method relies on a periodic excitation of the electron spin resonance by wide-band frequency sweeps at a kilohertz rate combined with a phase-locked detection of the photoluminescence signal. The technique is robust against changes in spectrum shape and photoluminescence intensity, and is readily extended by a frequency feedback to enable real-time tracking of the spin resonance. Fast scanning magnetometry is especially useful for samples where the signal dynamic range is large, of order millitesla, such as for ferromagnets or ferrimagnets. We demonstrate our method by mapping stray fields above the model antiferromagnet $\ensuremath{\alpha}$-${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ (hematite) at pixel rates of up to $100\phantom{\rule{0.2em}{0ex}}\mathrm{Hz}$ and an image resolution exceeding one megapixel.

Did we solve the old contradiction between microscopic and macroscopic experimental PFNS data?

Prompt Fission Neutron Spectra (PFNS) were analysed in the “dimensionless scale”. The important empirical facts were demonstrated. PFNS have the same shape for any isotopes and incident energy (<5MeV) for neutron induced and spontaneous fission. This is an additional argument for application of the scale method developed before. It was highlighted that spectrum shape changes slope at outgoing energy > 7 MeV. This fact was demonstrated with microscopic and macroscopic data. It was confirmed that old contradiction between microscopic and macroscopic data (mic-mac problem) has not yet been resolved.

Effect of the depolarization field on coherent optical properties in semiconductor quantum dots

We study the photon echo spectrum of self-assembled semiconductor quantum dots using femtosecond light pulses. The spectrum shape changes from a single-peaked to a double-peaked structure as the time delay between the two excitation pulses is increased. The spectrum change is reproduced by numerical calculations, which include the depolarization field induced by the biexciton-exciton transition as well as the conventional local-field effect for the exciton--ground-state transition in a quantum dot. Our findings suggest that various optical transitions in tightly localized systems generate a depolarization field, which renormalizes the resonant frequency with a change in the polarization itself, leading to unique optical properties.

1,4-Bis(2-methylstyryl)benzene doped PMMA fibre for blue range fluorescent applications

The fluorescent dyes allow new optical applications in polymer-based optical fibre technology. The article presents highly fluorescent 1,4-Bis(2-methylstyryl)benzene doped poly(methyl methacrylate) (PMMA) fibre. The multi-peak (422, 450, 488nm) fluorescence spectrum of the bulk specimen under 355nm excitation is presented. The polymerization and fibre drawing process is also shown. The fluorescent properties vs. fibre length at excitation 405nm are investigated. Significant spectrum shape changes and red shift phenomena of individual peaks are presented using one end excitation and fibre cutting method measurements for fibre length 2–90cm. Obtained attenuation level 0.69dB/m limits useful fibre length but obtained results can be useful in new polymeric fibers applications (e.g. sensors, light sources).

Using Real-Time Quantification of Autofluorescence Spectrum Shape to Distinguish between Metabolic Responses Involving Nadh-Utilizing Pathways

In recent studies, autofluorescence measurement of excited-state lifetime or anisotropy decay have revealed multiple forms (e.g., conformations) of intracellular NADH. Because proportions of these forms respond differently to metabolic conditions, the often-used “free” and “protein bound” assignments for NADH may not be adequately descriptive, possibly leading to ambiguities when identifying metabolic state. Here, we describe an accessible method for sensing changes in cellular NADH forms, based on the real-time tracking of UV-excited autofluorescence spectrum shape quantified using spectral phasor analysis. The analytic power of a phasor approach is utilized, testing for whether changes in spectrum shape are consistent with two-state behavior. We show that spectral phasor quantification of spectrum shape can distinguish between metabolic responses induced by the additions of cyanide, glucose, and various alcohols to Saccharomyces cerevisiae suspensions. Controls are presented, evidencing the physiological origins of these spectral responses. The potential for measuring dynamical aspects of metabolic responses, e.g., in relation to Crabtree-positive overflow metabolism and to cellular respiratory activity, is discussed.

Rescuing the nonjet (NJ) azimuth quadrupole from the flow narrative

According to the flow narrative commonly applied to high-energy nuclear collisions a cylindrical-quadrupole component of 1D azimuth angular correlations is conventionally denoted by quantity $v_2$ and interpreted to represent elliptic flow. Jet angular correlations may also contribute to $v_2$ data as "nonflow" depending on the method used to calculate $v_2$, but 2D graphical methods are available to insure accurate separation. The nonjet (NJ) quadrupole has various properties inconsistent with a flow interpretation, including the observation that NJ quadrupole centrality variation in A-A collisions has no relation to strongly-varying jet modification ("jet quenching") in those collisions commonly attributed to jet interaction with a flowing dense medium. In this presentation I describe isolation of quadrupole spectra from pt-differential $v_2(p_t)$ data from the RHIC and LHC. I demonstrate that quadrupole spectra have characteristics very different from the single-particle spectra for most hadrons, that quadrupole spectra indicate a common boosted hadron source for a small minority of hadrons that "carry" the NJ quadrupole structure, that the narrow source-boost distribution is characteristic of an expanding thin cylindrical shell (strongly contradicting hydro descriptions), and that in the boost frame a single universal quadrupole spectrum (L\'evy distribution) on transverse mass $m_t$ accurately describes data for several hadron species scaled according to their statistical-model abundances. The quadrupole spectrum shape changes very little from RHIC to LHC energies. Taken in combination those characteristics strongly suggest a unique {\em nonflow} (and nonjet) QCD mechanism for the NJ quadrupole conventionally represented by $v_2$.

Excitation of surface and volume plasmons in a metal nanosphere by fast electrons

Collective multipole oscillations (surface and volume plasmons) excited in a metal nanosphere by moving electron and corresponding inelastic scattering spectra are studied based on the hydrodynamic approach. Along with the bulk (dielectric) losses traditionally taken into account, the surface and radiative ones are also considered as the physical mechanisms responsible for the plasmon damping. The second and third mechanisms are found to be essential for the surface plasmons (at small or large cluster radii, respectively) and depend very differently on the multipole mode order. The differential equations are obtained which describe the temporal evolution of every particular mode as that one of a linear oscillator excited by the given external force, and the electron energy loss spectra are calculated. The changes in spectrum shape with the impact parameter and with the electron passage time are analyzed; the first of them is found to be in good enough agreement with the data of scanning transmission electron microscopy experiments. It is shown that, in the general case, a pronounced contribution to the formation of the loss spectrum is given by the both surface and volume plasmons with low and high multipole indices. In particular, at long electron passage time, the integral (averaged over the impact parameter) loss spectrum which is calculated for the free-electron cluster model contains two main peaks: a broad peak from merging of many high-order multipole resonances of the surface plasmons and a narrower peak of nearly the same height from merged volume plasmons excited by the electrons that travel through the central region of the cluster. Comparatively complex dependences of the calculated excitation coefficients and damping constants of various plasmons on the order of the excited multipole result in wide diversity of possible types of the loss spectrum even for the same cluster material and should be taken into account in interpretation of corresponding electron energy loss spectroscopy experiments.

Variation of focal switch with spectrum of a broadband laser

Effects of the spectrum on focal switch of a broadband laser in a dispersion dual-focus system are presented in this paper. The numerical results show that the two maximum intensities of the broadband laser on the z-axis vary when the central frequency of the broadband laser shifts and the spectrum shape changes, and the variations affect the generation of the focal switch. It is also found that difference of the two maximum intensities tends to increase when the absolute value of central wavelength increases. According to the results in this paper, the generation of the focal switch can be controlled by choosing the shift of the central frequency, the bandwidth, the distance between the two lenses, and the spectrum shape of the broadband laser.

Autofluorescence from NADH Conformations Associated with Different Metabolic Pathways Monitored Using Nanosecond-Gated Spectroscopy and Spectral Phasor Analysis

Cellular NADH conformation is increasingly recognized as an endogenous optical biomarker and metabolic indicator. Recently, we reported a real-time approach for tracking metabolism on the basis of the quantification of UV-excited autofluorescence spectrum shape. Here, we use nanosecond-gated spectral acquisition, combined with spectrum-shape quantification, to monitor the long excited-state lifetime autofluorescence (usually associated with protein-bound NADH conformations) separately from the autofluorescence signal as a whole. We observe that the autofluorescence response induced by two NADH-oxidation inhibitors—cyanide and ethanol—are similar in Saccharomyces cerevisiae when monitored using time-integrated detection but easily distinguished using time-gated detection. Results are consistent with the observation of multiple NADH conformations as assessed using spectral phasor analysis. Further, because well-known oxidation inhibitors are used, changes in spectrum shape can be associated with NADH conformations involved in the different metabolic pathways, giving bioanalytic utility to the spectral responses.

Dimensionality and noise in energy selective x‐ray imaging

To develop and test a method to quantify the effect of dimensionality on the noise in energy selective x-ray imaging. The Cramèr-Rao lower bound (CRLB), a universal lower limit of the covariance of any unbiased estimator, is used to quantify the noise. It is shown that increasing dimensionality always increases, or at best leaves the same, the variance. An analytic formula for the increase in variance in an energy selective x-ray system is derived. The formula is used to gain insight into the dependence of the increase in variance on the properties of the additional basis functions, the measurement noise covariance, and the source spectrum. The formula is also used with computer simulations to quantify the dependence of the additional variance on these factors. Simulated images of an object with three materials are used to demonstrate the trade-off of increased information with dimensionality and noise. The images are computed from energy selective data with a maximum likelihood estimator. The increase in variance depends most importantly on the dimension and on the properties of the additional basis functions. With the attenuation coefficients of cortical bone, soft tissue, and adipose tissue as the basis functions, the increase in variance of the bone component from two to three dimensions is 1.4 × 10(3). With the soft tissue component, it is 2.7 × 10(4). If the attenuation coefficient of a high atomic number contrast agent is used as the third basis function, there is only a slight increase in the variance from two to three basis functions, 1.03 and 7.4 for the bone and soft tissue components, respectively. The changes in spectrum shape with beam hardening also have a substantial effect. They increase the variance by a factor of approximately 200 for the bone component and 220 for the soft tissue component as the soft tissue object thickness increases from 1 to 30 cm. Decreasing the energy resolution of the detectors increases the variance of the bone component markedly with three dimension processing, approximately a factor of 25 as the resolution decreases from 100 to 3 bins. The increase with two dimension processing for adipose tissue is a factor of two and with the contrast agent as the third material for two or three dimensions is also a factor of two for both components. The simulated images show that a maximum likelihood estimator can be used to process energy selective x-ray data to produce images with noise close to the CRLB. The method presented can be used to compute the effects of the object attenuation coefficients and the x-ray system properties on the relationship of dimensionality and noise in energy selective x-ray imaging systems.

발광 스펙트럼 제어를 통한 표준광원 A 대체형 LED 개발

In this study, a standard illuminant A type LED that has similar emission spectrum as the standard illuminant A was developed using LED chip(emission peak: 405[nm]) and four types of phosphors(blue, green orangered and red). Using the design of experiment for spectrum control, the trend of the change of spectrum shape influenced by the change of interaction among phosphors and their density could be examined. Computer simulation through the optimization of the design of experiment revealed that, among four phosphors, the most influential one on the shape of the spectrum was green phosphor. Using the obtained optimal combination ratio of the four phosphors, an alternative LED illuminant to the actual standard illuminant A was developed and the spectrums of these two were confirmed identical. Using this standard illuminant A type LED, a portable transmittance meter with the range of measurement error of ±1.0[%] was developed.

Reflection properties of coupled-ring reflectors

The reflection properties of a coupled-ring reflector (CRR) are analyzed using the transfer matrix method. The CRR is composed of two coupled rings that are coupled to a bus waveguide. Depending on the combination of the cross-coupling ratios of the couplers, the reflection spectrum shape changes greatly. In the lossless case, the reflection spectrum has four peaks when the ring-bus coupling ratio is small. When the ring-bus coupling ratio is more than half and the ring-ring coupling is very small, the four peaks broaden, forming a single peak with still considerably narrow reflection spectrum, which makes the CRR attractive in applications requiring compact reflectors such as for single-mode laser diodes. The dependence of the propagation and insertion losses of the couplers on the reflection spectrum is also investigated, and the design guidelines are presented.

Comparison of measured and modeled stratospheric UV/Visible actinic fluxes at large solar zenith angles

Measured and modeled stratospheric filter sensitivity weighted ultraviolet/visible (UV/vis) actinic fluxes—approximating the NO2 photolysis rate coefficients (jNO2)— are compared. The measurements were performed with two calibrated 2π‐actinometers assembled on the azimuth angle‐controlled LPMA/DOAS (Laboratoire de Physique Moléculaire et Applications/Differential Optical Absorption Spectroscopy) gondola during a series of balloon flights. Since the actinometer's spectral sensitivity curve did not exactly match the actinic spectrum of NO2 and the skylight's spectrum shape changes with atmospheric height and solar illumination, only proxies (proxy‐)jNO2 rather than true jNO2 values were monitored during balloon ascents (0–30 km) for solar zenith angle (SZA) 75° &lt; SZA &lt; 86°, and at balloon float altitude during solar occultation (86° &lt; SZA &lt; 95°). The measured direct and diffuse total proxy‐jNO2 values compare excellently with radiative transfer (RT) modeling. That finding allows us to rule out uncertainties in computing UV/vis actinic fluxes as a significant factor in the still insufficient modeling of stratospheric NO2 at large SZAs.

Photoinduced luminescence quenching and insolubilization of star-like branched organosilicon compounds

Soluble star-like branched organosilicon compounds having silanylene and oligothienylene in their arms are stable in vacuum upon light irradiation, and remain highly light emissive, but degrade upon light irradiation in air. Though the change of absorption spectrum upon light irradiation is not so large, photoluminescence (PL) intensity is strongly suppressed without notable change in spectrum shape. Remarkable shortening of PL decay time due to degradation upon light irradiation in air has been confirmed by time-resolved PL measurement. These results are discussed in terms of scission of Si–Si bonds and oxidation. Optical recording utilizing photoinduced insolubilization of these materials has also been demonstrated.

Micro-probed raman scattering in La2-xSrxCuO4

Abstract The two-magnon scattering peak in La2-x Sr x CuO4 single crystals has been investigated by using a micro-probed Raman scattering technique. The peak intensity and the shape of two-magnon scattering are very sensitive to the Sr concentration. In La2CuO4, a micro analysis of the two-magnon scattering has been carried out as a function of position on the surface of the sample crystal. The peak frequency of two-magnon peak moves slightly, about 156 cm−1, without any change of spectrum shape as the observation position sweeps from 0 to 50 μm. On the other hand, the phonon peak does not show any anomalies. Furthermore, EPMA data shows that local compositions of Cu and La atoms distribute about 2% in the observed region of the sample. It suggests that the magnetic spin fluctuation is essentially affected by the local structure of the sample.

Inner-shell energy loss spectroscopy under reflection-microscopy condition

Electron energy loss spectroscopy(EELS) of the inner shells of atoms is now a well established technique for determination of specimen composition, especially for the light elements. In recent years there has been a revival interest in reflection electron microscopy(REM) as a method for examining surface morphology. It would be useful if the techniques of bulk microanalysis could also be applied in reflection mode. The first electron microscope reflection energy loss measurement were due to Krivanek et al. They successfully showed the enhancement of the surface plasmon in silicon but the Si L edge at 100eV could only be seen as a change in spectrum shape. This is a characteristic of multiple scattering and it is hardly surprising that it should be more important in REM. Multiple scattering in TEM limits energy loss to relatively thin regions, but even under conditions in which multiple scattering has eliminated a low energy edge (such as Si L) the edge of a deep inner shell with binding energy greater than 1 kV can still be clearly seen, though sometimes distorted in shape.

Spectrum shape changes of solvated electrons in 1-octanol

Spectrum shape changes of solvated electrons in 1-octanol

A universal Gamma-gamma method for simultaneous determination of rock and ore properties

A method for the simultaneous determination of heavy element content, density, borehole diameter and grain size is described, which is based on investigation of the changes in spectrum shape. By analysing these changes in a quantitative manner, information regarding the physical parameters of the medium can be obtained. The results of laboratory tests of the method are presented.

The emission spectra of NaD 2O, InBe, LaBe and NaBe photoneutron sources

The energy distribution of the photoneutrons of NaD 2O, InBe, LaBe and NaBe source systems were measured by means of a proton-recoil proportional counting tube. Spherical lead-shields of various thicknesses (ranging from 1·5 to 13 cm) were used to reduce the intense gamma field accompanying the neutron spectra to be measured. The spectra of spherical heterogeneous source arrangements for three different Be-target thicknesses (0·5, 1· and 2·0 cm) were measured and compared with the theoretical distribution as obtained by Monte-Carlo calculations. The change in spectrum shape due to the lead shields was also calculated by a Monte-Carlo routine. Good agreement between theoretical predictions and experimental results shows values for the peak of the neutron distribution of 264·1 ± 0·5 keV for the NaD 2O system, 397·3 ± 0·8 keV for the InBe system, 761·7 ± 0·7 keV for the LaBe system, and 966·9 ± 0·5 keV for the NaBe source system. With the LaBe system a second neutron group of much lower intensity (6·5 per cent of the main group) could be found with a peak energy of 1097·5 +- 1·0 keV in good agreement to recent gamma-spectroscopic measurements.

Measurement ofρoandφ-Meson Electroproduction

We report measurements of ${\ensuremath{\rho}}^{0}$ and $\ensuremath{\varphi}$ electroproduction at 19.5 GeV in a wide-aperture spectrometer which detected the scattered electron and the decay products of the vector mesons. Data are presented for the region of virtual-photon mass squared ${q}^{2}=\ensuremath{-}0.25 \mathrm{to} \ensuremath{-}2.0$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ and virtual-photoproduction center-of-mass energy squared $s=10 \mathrm{to} 30$ Ge${\mathrm{V}}^{2}$. As $|{q}^{2}|$ increases, the $\ensuremath{\rho}$ mass spectrum shape changes and the momentum-transfer distribution broadens. The ratio of the $\ensuremath{\rho}$ cross section to the total cross section decreases from 11% at ${q}^{2}=0$ to about 6% at $|{q}^{2}|={{m}_{\ensuremath{\rho}}}^{2}$. The ratio for the production of longitudinally to transversely polarized ${\ensuremath{\rho}}^{0}$ mesons is ${0.45}_{\ensuremath{-}0.10}^{+0.15}$ at $|{q}^{2}|={{m}_{\ensuremath{\rho}}}^{2}$, and the interference between longitudinal and transverse amplitudes is almost maximal. The relative $\ensuremath{\varphi}$-meson cross section also decreases as $|{q}^{2}|$ increases. Unitary lower bounds on the longitudinal-transverse ratio in inelastic electron scattering are derived.