Identification of Three Weak Lines and Their Influences on Diagnostics of Electron Temperature and Density in Astrophysical Plasmas

By comparing of the spectra from the Chandra LETGs observation with the synthetic spectra of argon, we identify two weak emission lines, that is, the Ar XV 27.470A line with transition 2s3p ^1p1 - 2s^2 ^1So and the Ar XVI 27.872A line with transition 3d ^2D3/2 - 2p ^2P1/2, which blend with the N Ⅶ Lyα emission line. Several secondorder spectral lines are also identified, one of which is the second-order Fe XⅧ 14.534A line with transition 2p^4(^3p)3d ^2F5/2 - 2p^5 ^2P3/2, which blends with the inter-combination line of He-like N VI. In order to study the effects of these new identified weak lines on the electron temperature and density, we diagnose the two parameters using the intensity ratio of triplets of the He-like N Ⅵ and that of resonance lines of H- and He-like N. In the literature, there is a discrepancy of the temperatures deduced from N Ⅵ from other He-like ions, such as C V and O Ⅶ. The discrepancy disappears after the contribution of these weak lines is taken into account.     

Application of electric field ionization method to detect the high-lying Rydberg states of Eu I

The 4f~76s(~9S)np 8 P J (J = 5/2, 7/2, 9/2) Rydberg series converging to the first ionization limit 4f 7 6s 9 S 4 of the Eu atom using the three-step laser excitation and electric-field-ionization (EFI) method are studied. First, the Eu atom is excited from the 4f 7 6s 2 8 S o 7/2 ground state to the 4f 7 6s7s 8 S o 7/2 state through the 4f 7 6s6p 10 P 9/2 state by the first two dye lasers. Next, it is populated to many higher-n members of the 4f 7 6s( 9 S)np 8 P J Rydberg series by the third dye laser whose wavelength is scanned within a certain range. Finally, the atom in these higher-n states is ionized by the external pulsed electric field. With the field strength up to 2 kV/cm, we can detect the atom in 4f 7 6s(9 S)np 8 P J states with n 40. With the given laser line width, the level energies of Rydberg states with n as high as 72 can be determined. We not only confirm the previous data on the 4f 7 6s(9 S) np 8 P J Rydberg series, but also extend the n-value assignment significantly by detecting more states.     

Low—Lying Resonance States of Slow Electron Collisions With Atomic Oxygen

A 39-target state close-coupling calculation of low-energy electron scattering from atomic oxygen is carried out with core-valence electron correlation by using R-matrix method. It is shown that the elastic cross section has a huge and sharp increase with the electron energy going down below 1eV. This remarkable structure is attributed to a few very low-lying potential resonances and the features of these resonances are given with partial cross sections. It is also shown that after considering excitations of two electrons from 2s shell, the three lowest atomic energy levels are in agreement with experimental results better than that just considering excitations of two electrons from the 2p shell as well as only one electron from the 2s shell. Elastic and two excitation (^3P→^1D and ^3P→^1S) cross sections are given and compared with the other theoretical and experimental results.     

Investigation of odd-parity Rydberg states of Eu I with autoionization detection

Isolated-core-excitation (ICE) scheme and autoionization detection are employed to study the bound Rydberg states of europium atom. The high-lying states with odd parity have been measured using the autoionization detection method with three different excitation paths via 4f⁷6s6p[ ⁸P_5/2], 4f⁷6s6p[ ⁸P_7/2] and 4f⁷6s6p[ ⁸P_9/2] intermediate states, respectively. In this paper the spectra of bound Rydberg states of Eu atom are reported, which cover the energy regions from 36000~cm^-1 to 38250~cm^-1 and from 38900~cm^-1 to 39500 cm^-1. The study provides the information about level energy, the possible J values and relative line intensity as well as the effective principal quantum number n^* for these states. This work not only confirms the previous results of many states, but also discovers 11 new Rydberg states of Eu atom.     

The VMI study on angular distribution of ejected electrons from Eu 4f~76p_(1/2)6d autoionizing states

The combination of a velocity mapping imaging technique and mathematical transformation is adopted to study the angular distribution of electrons ejected from the Eu 4f76p1/26 d autoionizing states, which are excited with a three-step excitation scheme via different Eu 4f76s6d8 D J(J = 5/2, 7/2, and 9/2) intermediate states. In order to determine the energy dependence of angular distribution of the ejected electrons, the anisotropic parameters are measured in the spectral profile of the 6p1/26 d autoionizing states by tuning the wavelength of the third-step laser across the ionic resonance lines of the Eu 6s+→ 6p+. The configuration interaction is discussed by comparing the angular distributions of ejected electrons from the different states. The present study reveals the profound variations of anisotropic parameters in the entire region of autoionization resonance, highlighting the complicated nature of the autoionization process for the lowest member of6p1/26 d autoionization series.     

EXCITATION OF 5dnd（J=4） AUTOIONIZING STATES OF BARIUM BY MEANS OF MULTISTEP LASER DRIVING PLUS A SUPERRADIATION PROCESS AND MQDT ANALYSIS

In this work.superradiation in found to play an important role to populate the metastable level 6s5d ^1 D2 from which 5dnd(J=4) autoionizing Rydberg series were excited through double-resonant laser driving.Experimental results were analysed using 5-channel quantum defect treatment in which three autoionizing Rydberg series and two open channels were included.     

Photoluminescence Characterization of Silicon Nanoparticles Hybridized Europium Complex

A europium complex Eu (DBM)3 TPPO (Eu tris(benzoylmethide)-(triphenylphosphine oxide)) and silicon nanoparticles have been hybridized.The hybridization can evidently change the photoluminescence (PL) characteristics of the Eu complex in the following aspects:under an excitation of 390nm,the intensity of the PL peak at 611nm due to the ^5Du-^7F2 transition of the Eu^3 ions has been increased by 30%,and thc integrated PL intensity in the visible range has been increased by nearly 3 times;the PL excitation efficiency beyond 440nm has been improved cvidently;the peak in the PL excitation spectrum shifts from 408nm to 388nm,and the PL decay time decreases from 2.07 to 0.96μs,The experimental results indicatde that in the PL process,the photoexcited energy may transfer from the silicon nanoparticlcs to the Eu^3 ions.     

Measurement of hyperfine structure and isotope shifts in the 580.56nm line of 142－145,146,148,150Nd+

Isotope shifts and hyperfine spectrum of singly ionized neodymium ion was measured by collinear fast-ion-beam laser spectroscopy. The hyperfine A constants and B constants are obtained for the (23230)9/2^0 level and 4f^45d ^6K9/2 level, respectively. The optical isotope shifts between seven isotopes in the 580.56 nm of^142-145,146,148,150Nd^ line are determined. The configuration admixtures for (23230)9/2^0 level were quantitatively analysed to be 4f^46p, 4f^35d^2, and 4f^35d6p with mixing coefficients of 67%, 5%, and 28%, respectively.     

Enhanced Brightness of Eu^3＋ Complex in Organinc Electroluminescent Devices by Using Another Rare—Earth Ion

Rare-earth ions Tb^3 and La^3 were used as a bridge to improve the energy transfer from the polymer to an Eu complex.The material Tb(La)0.5Eu0.5(BSA)3 phen was synthesized and used as the emission layer in the device:ITO/PVK:Tb(La)0.5Eu0.5(BSA)3phen/Alq/Al.The two device were compared in detail and it was found that the device using La0.5Eu0.5(BSA)3phen as the emission material had better monochromatic characteristics with the maximal brightness of 102 ca/m^2 and the colour coordinates x=0.55 and y=0.36.     

An electron spin resonance study of Eu doping effect in La_(4/3)Sr_(5/3)Mn_2O_7 single crystal

The effect of Eu3+ion doping in the La sites of single-crystal La4/3Sr5/3Mn2O7was investigated. Electron spin resonance(ESR) was applied to La4/3Sr5/3Mn2O7and(La0.8Eu0.2)4/3Sr5/3Mn2O7single crystals. A phase separation and phase transitions were observed from the ESR spectra data. Between 350 K and 300 K, both paramagnetic resonance(PMR)and anisotropic ferromagnetic resonance(FMR) lines were observed in the ab plane and the c axis direction, suggesting a coexistence of the paramagnetic(PM) phase and the ferromagnetic(FM) phase. The magnetization measurement reveals a spin-glass-like behavior in single-crystal(La0.8Eu0.2)4/3Sr5/3Mn2O7below the temperature of spin freezing Tf(～ 29.5 K).     

Theoretical Investigation of Decay Process in a Doubly Excited 2s^2 ^1S0 State of He-Like Ions

In the framework of multi-configuration Dirac-Fock theory, a detailed calculation is performed for the decay rates and the energies of the doubly excited 2s^2 ^1So state of He-like ions, of which atomic number Z ranges from 6 to 92. The 2s^2 ^1So - ls ^2S1/2 Auger decay is predominant at low Z regime, whereas the 2s^2 ^1So - 1s2p ^1,3P1 two-electron one-photon transitions become quite important in moderate and high Z regimes. For heavy ions with Z ≥ 72, the contribution of 2s^2 ^1So - 1s2s ^3S1 M1 transition is significant. The Breit interaction considerably enhances the 2s^2 ^1So - 1s ^2S1/2 Auger rate at high Z regime.     

The application of sample-and-hold circuits in the laser frequency-shifting

Lasers with stable frequencies are essential in manyfields of research[1-4] such as in laser cooling andtrapping atoms[5] and Bose-Einstein condensationexperiments[6,7]. It is required that the line width oflasers is less than 1 MHz and does not have long-termdrift. Yet on some occasions, it is often necessary torapidly shift the frequencies of cooling beams from thedetuning -2Γ - 3Γ to -6Γ - 8Γ (Γ is the natural widthof the atom) to lower the temperature[8,9]. Normally, wehave two mean…     

Extreme ultraviolet and x-ray transition wavelengths in Rb XXIV

Energy levels, radiative rates, oscillator strengths and line strengths are reported for transitions among the lowest 97 levels of the(1s22s22p6) 3s23p2, 3s23p3 d, 3s3p3, 3p4, 3s3p23 d, and 3s23d2 configurations of Rb XXIV. A multiconfiguration Dirac–Fock(MCDF) method is adopted for the calculations. Radiative rates, oscillator strengths, and line strengths are provided for all electric dipole(E1), magnetic dipole(M1), electric quadrupole(E2), and magnetic quadrupole(M2)transitions from the ground level to all 97 levels, although calculations are performed for a much larger number of levels.To achieve the accuracy of the data, comparisons are provided with similar data obtained from the Flexible Atomic Code(FAC) and also with the available theoretical and experimental results. Our energy levels are found to be accurate to better than 1.2%. Wavelengths calculated are found to lie in EUV(extreme ultraviolet) and x-ray regions. Additionally, lifetimes for all 97 levels are obtained for the first time.     

Pressure-broadened atomic Li(2s-2p) line perturbed by ground neon atoms in the spectral wings and core

Full quantum calculations are performed to investigate the broadening profiles of the atomic lithium Li(2s-2p) resonance line induced by interactions with ground Ne(2s~22p~6) perturbers in the spectral wings and core. The X~2Σ~+, A~2Π,and B~2Σ~+ potential-energy curves of the two first low lying Li Ne molecular states, as well as the corresponding transition dipole moments, are determined with ab initio methods based on the SA-CASSCF-MRCI calculations. The emission and absorption coefficients in the wavelength range 550-800 nm and the line-core width and shift are investigated theoretically for temperatures ranging from 130 K to 3000 K. Their temperature dependence is analyzed, and the obtained results are compared with the previous experimental measurements and theoretical works.     

Temperature dependence of the photoluminescence of MnS/ZnS core–shell quantum dots

The temperature dependence of the photoluminescence（PL） from Mn S/Zn S core–shell quantum dots is investigated in a temperature range of 8 K–300 K. The orange emission from the ^4T1→^6A1transition of Mn^2＋ions and the blue emission related to the trapped surface state are observed in the Mn S/Zn S core–shell quantum dots. As the temperature increases, the orange emission is shifted toward a shorter wavelength while the blue emission is shifted towards the longer wavelength. Both the orange and blue emissions reduce their intensities with the increase of temperature but the blue emission is quenched faster. The temperature-dependent luminescence intensities of the two emissions are well explained by the thermal quenching theory.     

Radius of ^9C from the Asymptotic Normalization Coefficient

The asymptotic normalization coefficient (ANC) of^9C=^8B p deduced from S Li(d, p)^9 Li reaction is used to obtain the root-mean-square (rms) radius of the loosely bound proton in the ^9C ground state. We obtain (r^2)1/2 = 3.61 fm for the valence proton, which is significantly larger than the matter radius of ^9C. The probability of the valence proton outside the matter radius of ^9C is greater than 60%. The present work supports the conclusion that ^9C has a proton halo structure.     

Two ways of propeller recognition feature extraction

The analysis of the radiated noise of vessels given in this paper showssome strong superposed line components in low frequency speetrum below100Hz occurring at discrete frequencies which correspond with the rotationspeed of propeller shaft,or propeller blade frequency,or their harmonic fre-quencies.since the line components reflect propeller＇working characteristics,the propller＇s features can be extracted directly from low-frequency line com-ponents in addition to demodulated line component.So there are two ways toextract the features,one is direct way,the other is demodulation way.Detec-tion performance of the line component in background-noise is discussed inthis paper.The signal level is defined as the difrerence between the PDF＇s(Probability Density Function)mean of the peak of the line component andPDF＇s mean or the background-noise.In dircet way the signal level of the linecomponent is proportional to the signal noise ratio(S/N).In demodulationway the signal level of demodulated line component     

Experimental Test of the Non—reproducibility of Cross Sections in Dissipative Reactions

Two independent measurements of cross sections for the ^19F ^93Nb dissipative heavy ion collisions have been performed at incident energies from 100 to 108MeV in steps of 250keV.In the two measurements,two independently prepared targets were used.All other experimental conditions were identical in both experiments.The data indicate that non-reproducibility of the non-self-averaging oscillation is yielded in the two measurements.This supports the recent theoretical predictions of spontaneous coherence,slow phase randomization and extreme sensitivity in highly excited complex quantum systems.     

激光感生碰撞能量转移实验

首次观察到Eu(6s6p)^P9/2至Sr(5s10s)^1So、准稳态翼为紫翼的激光感生碰撞能量转移实验现象,其荧光波长为458.42nm,峰值转移激光波长为459.75nm,并对其激发函数谱随温度和随转移激光能量改变进行实验研究,测量了激光感生碰撞能量转移谱的截面,证实了激光感生碰撞能量转移谱为非对称谱。