Investigation of the J-TEXT plasma events by k-means clustering algorithm

Various types of plasma events emerge in specific parameter ranges and exhibit similar characteristics in diagnostic signals,which can be applied to identify these events.A semisupervised machine learning algorithm,the k-means clustering algorithm,is utilized to investigate and identify plasma events in the J-TEXT plasma.This method can cluster diverse plasma events with homogeneous features,and then these events can be identified if given few manually labeled examples based on physical understanding.A survey of clustered events reveals that the k-means algorithm can make plasma events(rotating tearing mode,sawtooth oscillations,and locked mode)gathering in Euclidean space composed of multi-dimensional diagnostic data,like soft x-ray emission intensity,edge toroidal rotation velocity,the Mirnov signal amplitude and so on.Based on the cluster analysis results,an approximate analytical model is proposed to rapidly identify plasma events in the J-TEXT plasma.The cluster analysis method is conducive to data markers of massive diagnostic data.

Reactions of Laser Ablation-magnesium Plasma with Methanol Clusters

The laser ablation-molecular beam（LA-MB） method is useful for studying the reactions of metal ions with molecular clusters. Reactions of magnesium plasma with methanol clusters were studied by using this method. A specially designed reaction cell was used as a fast flow reactor operated under thermal conditions, and the reaction products were measured with a time-of-flight（TOF） mass spectrometer. Surprisingly, several series of cluster ions with complex sizes and intensity distributions were obtained when the laser ablating was applied to different parts of the molecular beam. In the front part of the molecular beam, strong Mg^＋ （CH3OH）n（ n = 0-5） and weak H^＋ （CH3OH）n（ n = 0-5 ） cluster ions were observed with relatively small cluster sizes ; in the middle part of the molecular beam, the main cluster ions were H^＋ （ CH3OH）n （ n = 6-17 ） and H^＋（ H2O） 2 （ CH3OH）n（ n = 6-17 ） with a relatively large cluster size and a weak intensity; in the back part of the molecular beam, two new series of cluster ions, MgO^＋ （ H2O） （ CH3 OH）n（ n = 6-10 ） and MgOCH3^＋ （ CH3OH）n（ n = 6-10）, were obtained and accompanied by weak H^＋（CH3OH）n（n = 4-7） and H^＋（ H2O）2 （CH3OH）n（ n = 3-6）. The formation mechanisms and speed characteristics of the cluster ions are discussed in this article.

Configuration of 2D Finite Clusters in Plasma Sheath

Finite clusters with a small number of charged particles immersed in a plasma environment have been numerically simulated with a dynamic method. Finite Coulomb clusters are systems of a small number of charged particles, N = 1 to 100, confined by a potential produced by plasma 2D-sheath. Under the action of net force each particle is in an equilibrium position and together they form finite Coulomb clusters. The results of our study show the configuration of Coulomb clusters do not depend on their initial state. After theoretically studied and tested by using the Monte Carlo technique we also prove the system energy is the determinant parameter of the configuration. In addition, the effect of the external magnetic field on the cluster configuration is analyzed.

Dispersion relations of lattice waves in three-dimensional strongly coupled complex plasma crystals

Dispersion relation matrices, with the screened Coulomb interaction between a charged dust particle and all other particles taken into account, are derived for waves in body centred cubic （bcc） and face centred cubic （fcc） lattices in three-dimensional strongly coupled complex plasma crystals separately. The matrices are then calculated in characteristic directions to obtain the longitudinal and transverse eigenmodes. The longitudinal and transverse waves for these cases are discussed separately.

Building Crystals from Clusters

Ab initio total energy calculations are used to simulate the building of equiatomic solid APballoys (A=Li, Na, K) with A4Pb4 clusters which are particularly stable in the gas phase. Theeight clusters per unit cell were drawn together by shrinking the cell in stages, and allowingfull atomic relaxation at each stage. Charged Pb4 tetrahedral units dominate the structuraland electronic properties, and these units are remarkably robust and insensitive to their alkalienvironment. The stability of the Pb4 units diminishes as we progress from K to Li and lead totheir absence in the LiPb alloy in accordance with experiment. The distance between Pb4 unitsseems to be the critical factor responsible for the structural trends, which is determined by theatomic size of the alkali.

Vicinage Effects for a Nitrogen Molecular Cluster in Plasmas

The vicinage effects are studied for a fast nitrogen diatomic molecular cluster in a high-density plasma target.A variety of plasma parameters are discussed with regard to stopping power ratio,molecular axis deflection and Coulomb explosion.Emphasis is placed on the vicinage effects on Coulomb explosion and stopping power for a nitrogen cluster in plasmas.The results indicate that vicinage effects influence the correlation between ions in the cluster,and the Coulomb explosion will proceed faster with higher projectile speed,lower plasma density and higher plasma temperature.Comparing hydrogen and nitrogen molecular ions for Coulomb explosion and deflection angle under the same set of parameters,one can find that the nitrogen ion has faster Coulomb explosion and stronger deflection of molecular axis due to the contribution of charge.In the initial stage of the Coulomb explosion the stopping power ratio has a higher value due to enhanced vicinage effects while in the later stage the stopping power ratio approaches one,indicating that the vicinage effects disappear and the ions in the cluster simply behave as independent atomic ions in the plasma.

Ionization Induced Scattering of Femtosecond Intense Laser Pulses in Cluster Plasmas

The 45° scattering of a femtosecond (60 fs) intense laser pulse with a 20 nm FWHM (the full width at half maximum) spectrum centered at 790 nm has been studied experimentally while focused in argon clusters at intensity - 1016 W/cm2. Scattering spectra under different backing pressures and laser-plasma interaction lengths were obtained, which showed spectral blueshifting, beam refraction and complex modulation. These ionization-induced effects reveal the modulation of laser pulses propagating in plasmas and the existing obstacle in laser cluster interaction at high laser intensity and high electron density.

Synthesis, Crystal Structure and Spectroscopic Properties of an Octanuclear V-S-Cu Cluster {V_2S_6Cu_6}(PPh_3)_6(O)_2·2CH_2Cl_2·CH_3OH with a Metal-sulfur Dodecahedral Cage

A new octanuclear VSCu cluster {V2S6Cu6}(PPh3)6(O)22CH2Cl2CH3OH 1 has been prepared by extraction with CH2Cl2 of a solid mixture of (NH4)3VS4, Cu(PPh3)2Cl and NEt4Br, and its structure has been determined by single-crystal X-ray diffraction. Crystallographic data: C111H98Cl4Cu6O3P6S6V2, Mr = 2248.99, triclinic space group P , a = 13.751(6), b = 15.509(4), c = 15.642(5) ? a =114.34(2), b = 98.35(3), g = 110.43(3) , V = 2679.83 3, Z = 1, Dc = 1.538 g/cm3, F(000) = 1262, m (MoKa) = 16.9 cm-1, the final R = 0.079 and Rw = 0.083 for 5504 observed reflections with I > 2s(I). The structural determination shows that the skeleton can be described as a metal-sulfur dodecahedral cage fused by two incomplete cubane-like [VS3Cu3] subunits centrosymmetrically connected by CuS and weak CuCu bonds. The six copper and two vanadium atoms display a slightly distorted cubic array with a m4-S atom on each face of the metal cube. The selected IR, electronic and 51V NMR spectra have also been reported.

Syntheses and Crystal Structures of Two Heterobimetallic Clusters [WOS_3Cu_3I(dmpzm)_2]·2(MeCN)_(0.5) and [WS_4Cu_4I_2(dmpzm)_2]·DMF(dmpzm=Bis(3,5-dimethylpyrazolyl)methane)

The reaction of [Et4N]2WOS3 with three equiv.of CuI and dmpzm in MeCN afforded [WOS3Cu3I（dmpzm）2]·2（MeCN）0.5（1·2（MeCN）0.5） while that of [PPh4]2WS4 with four equiv.of CuI in DMF/MeCN followed by the addition of two equiv.of dmpzm in MeOH gave rise to [WS4Cu4I2（dmpzm）2]·DMF（2·DMF）.Both compounds were characterized by elemental analysis,IR,and single-crystal X-ray diffraction analysis.1·2（MeCN）0.5 crystallizes in triclinic,space group P1-with a = 11.4552（5）,b = 11.6735（3）,c = 16.2278（9） ,α = 99.537（9）,β = 101.986（2）,γ = 118.464（13）o,V = 1775.5（3）3,Z = 2,μ = 6.080 mm-1,Dc = 1.983 Mg/m3,T = 193（2） K,C24H35Cu3IN9OS3W,Mr = 1063.22,F（000） = 1018,S = 1.060,R = 0.0376 and wR = 0.0870.2·DMF belongs to the orthorhombic system,space group Pmn21 with a = 22.145（4）,b = 11.464（2）,c = 7.7370（15） ,V = 1964.2（6）3,Z = 2,μ = 6.865 mm-1,Dc = 2.189 Mg/m3,T = 193（2） K,C25H39Cu4I2N9OS4W,Mr = 1301.72,F（000） = 1226,R = 0.0632,wR = 0.1706 and S = 1.130.1·2（MeCN）0.5 consists of one CuI and two [Cu（dmpzm）]＋ fragments that are linked by [WOS3]2-species via six Cu-S bonds,forming a nido-like [WS3Cu3] core.2·DMF contains a saddle-shaped [WS4Cu4] core with two iodides coordinated at two Cu centers in a cis position and two dmpzm ligands being chelated at another two Cu centers in a cis position.

Probing the effects of lithium doping on structures, properties, and stabilities of magnesium cluster anions

Bimetallic clusters have aroused tremendous interest because the property changes like structure,size,and composition have occurred.Herein,a structural search of the global minimum for anionic LiMg_(n)^(-)(n=2-11) clusters is performed using an efficient crystal structure analysis by particle swarm optimization(CALYPSO) structural searching program with subsequent density functional theory(DFT) calculations.A great variety of low energetic isomers are converged,and the most stable ones are confirmed by comparing their total energy of each size.It is found that the LiMg_(n)^(-)clusters are structurally consistent with corresponding Mg clusters anions except for LiMg_(5)^(-)and LiMg_(7)^(-).In all the doped clusters,the Li atom prefers to occupy the convex position.Simulated photoelectron spectra(PES),Infrared(IR),and Raman spectra of LiMg_(n)^(-)could be used as an essential evidence for identifying cluster structures experimentally in the future.Stability study reveals that a tower-like structure of LiMg_(9)^(-)has prominent stability and can be identified as a magic number cluster.The reason might be that there are both closed-shell 1S^(2)1P^(6)1D^(10)2S^(2) electronic configurations and stronger Li-Mg bonds caused by sp hybridization in the LiMg_(9)^(-)cluster.

Synthesis and Crystal Structure of a Hexameric Organooxotin Cluster from Benzilic Acid

The title complex [^n BuSn（O）O2C（OH）CPh2]6.2H2O has been synthesized by the reaction of n-BuSn（O）OH with benzilic acid in 1：1 molar radio and characterized by IR, ^1H NMR spectra and elemental analysis. The crystal structure was determined by X-ray diffraction. It crystallizes in triclinic, space group PI with a = 1.3543（2）, b = 1.4593（2）, c = 1.5293（2） nm, α = 102.075 （2）,β = 115.571 （2）, γ = 93.308（3）°, Z = 1, V = 2.6282（7） nm^3, Mr = 2550.21, Dc = 1.611 g/cm^3,μ = 1.477 mm^-1, F（000） = 1280, R = 0.0309 and wR = 0.0729. The structure shows a distorted octahedral configuration with six-coordination for the central tin atom.

Synthesis and Crystal Structure of an Incomplete Cubane-like Heterobimetallic Cluster [（η^5-C5Me5）2Mo2（μ3-S）（μ-S）3（CuCl）]

The reaction of[（η^5-C5Me5）2Mo2（μ3-S）（μ-S）3（CuCl）]1 with Na2S in MeCN produced a trinuclear cluster [（η^5-C5Me5）2Mo2（μ3-S）（μ-S）3（CuCl）] 2. 2 crystallizes in the monoclinic system, space group P21/c with a = 15.563（3）, b = 8.9547（18）, c = 17.846（4） A, β = 101.29（3）°, V = 2438.9（9） A^3, Z = 4, Dc = 1.878 g/cm^3, T = 193（2） K, C20H30ClCuMo2S4, Mr = 689.60, F（000） = 1376, μ（MoKa） = 2.335 mm ^-1, S = 1.050, R = 0.0305 and wR = 0.0688 for 4033 observed reflections with I 〉 20-（I）. In the structure of 2, one [（η^5-C5Me5）2Mo2（μ-S）2S] moiety and one CuCI unit are assembled into an incomplete cubane-like [Mo2S4Cu] core framework, in which the Cu center adopts a distorted tetrahedral geometry coordinated by one ,μ3-S atom, two μ-S atoms and one terminal chloride. The two Mo…Cu contacts are 2.7519（7） and 2.7689（8） A, respectively.

Synthesis and Crystal Structure of an Octa-nuclear V-Cu-S Cluster:[VS_3O(CuPBu_3)_2(CuSPBu_3)]_2

The title compound has been synthesized by reaction of (NH4)3VS4,CuCl, and PBu3 in CH2Cl2 and its structure was determined by single crystal X-raydiffraction. Crystallographic data: C72 H162 Cu6O2P6S8V2, Mr= 1985. 57, monoclinicspace group C2/c, a= 17. 864(3), b= 25. 946(8), c= 24.071 (7),β= 112. 79(2)°,V = 10285. 9, Z= 4, Dc= 1. 28 g/cm3, F(000) = 4192, μ(MoKa) = 16. 7 cm-1,the final R=0.065 and Rw =0.074 for 4051 unique reflections with I> 3σ(I). Thestructure can be described as a metal-sulfur dodecahedral cage fused by two incompletecubane-like VS3Cu3 units connected by Cu - S bonds. The Cu - S bonds within theasymmetric VS3Cu3 unit are slightly shorter than those linking the two centrosymmetrically related VS3Cu3 units. The six copper and two vanadium atoms display asomewhat distorted cubane array with a μ4-S atom on each face of the metal cubane.

Synthesis and Crystal Structure of Mixed Mo-W Cubane-type Cluster Compound [Mo_2W_2S_4 (μ-OAc)_2 (dtp)_3(dtpH)]·CH_2Cl_2

The cubane-type mixed Mo W cluster[Mo2W2S4 (OAc)2(dtp)3 (dtpH)]·CH2Cl2 (dtp= (EtO)2PS2, dtpH = (EtO)2PS (SH) has been prepared by reduction and addition reaction between dinuclear W2S4 (dtp)2 and Mo(CO)6 in HOAc and Ac2O solution in the presence of dtp-ligand. Crystallographic data: Mr=1632. 71,monoclinic, space group P2/n, a=13. 146 (8), b=11. 961 (5),c=17. 157 (9) β =105. 99(8)°, V=2593(8), Z=2, Dc=2. 09 /cm￣3 ,λ(MoKa) =0.71073 ,F (000)=1578, final R=0. 029, Rw = 0. 041 for 3765 unique intensity data [I≥4σ (I)]. The result of X-ray study and elemental analysis indicated that, in the crystal lattice, molybdenum and tungsten are statistically distributed in the metal positions each with 0. 5 fractional occupation.

A Reflectron Time-of-Flight Mass Spectrometer with a Nano-Electrospray Ionization Source for Study of Metal Cluster Compounds

An experiment facility has been set up for the study of metal cluster compounds in our laboratory, which consists of a nano-electrospray ionization source, an ion transmission and focus system, and a reflectron time-of-fight mass spectrometer. Taking advantage of the nano-electrospray ionization source, polyvalent ions are usually produced in the ＂ionization＂ process and the obtained mass resolution of the equipment is over 8000. The molecular ion peaks of metal cluster compounds [Au20（PPhpy2）10Cl2]（SbF6）4, where PPhpy2=bis（2- pyridyl）phenylphosphine, and [AuaAg2（C）L6]（BF4）4, where L=2-（diphenylphosphino）-5- methylpyridine, are distinguished in the respective mass spectrum, accompanied by some fragment ion peaks. In addition, the mass-to-charge ratios of the parent ions are determi- nated. Preliminary results suggest that the device is a powerful tool for the study of metal cluster compounds. It turns out that the information obtained by the instrumentation serves as an essential supplement to single crystal X-ray diffraction for structure characterization of metal cluster compounds.

Structure and Luminescence Property of a Hexanuclear Silver(I) Cluster Containing Pyridine-3-carboxaldehyde Thiosemicarbazone

A new hexanuclear silver（I） compound containing thiosemicarbazone with group of 3-pyridine was synthesized and structurally characterized by single-crystal X-ray diffraction,elemental analysis and fluorescence spectrum.The title compound 3 crystallizes in monoclinic,space group C2/m with a = 18.6523（9）,b = 24.7519（11）,c = 22.4542（15） ,β = 93.4960（10）°,V = 10347.4（10）3,C68H104Ag6N30O8S6,Mr = 2309.39,Dc = 1.482g/cm3,μ（MoKα） = 1.293 mm-1,F（000） = 4656,Z = 4,the final R = 0.0544 and wR = 0.1580 for 6733 observed reflections（I 〉 2σ（I））.In the structure,two Ag6L36（L3 = pyridine-3-carboxaldehyde thiosemicarbazone） clusters are contained.In each cluster,the S atom of ligand L3 served as a triply bridged chelator to connect the six silver atoms into a Ag6L36 cluster.Luminescence investigation revealed that the band at 630 nm was attributed to cluster-centered（CC） electron transfer,and those at 493 and 530 nm to the LMCT and CC transitions,respectively.

Synthesis,Structure and Fluorescent Property of a New Isolated Zn6Co9 Heteronuclear Cluster Constructed by Four Kinds of Ligands

A novel zero-dimensional heteronuclear cluster based on N-（phosphonomethyl）imi- no-diacetic acid （H4PMIDA） and Phen （1,10-phenanthroline）, [Zn6Co9（PMIDA）6（Phen）6（NO3）4（H2O）6]·2NO3·16H2O, has been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectrum, thermal analysis, and single-crystal X-ray diffraction. The isolated 15- nuclearity cluster [Zn6Co9（PMIDA）6（Phen）6（NO3）4（H2O）6]^2＋ was constructed by four kinds of ligands, and its charges are balanced by NO3^–. Each isolated cluster is further extended into a 3D supramolecular network through π？？？π interaction and C–H…O hydrogen bonds. Moreover, the solid-state fluorescent property of this complex has also been investigated at room temperature.

Structure and Luminescence Property of a Hexanuclear Silver(Ⅰ) Cluster Containing Benzaldehyde Thiosemicarbazone

A new hexanuclear silver （I） compound 2 containing thiosemicarbazone with the group of benzene was synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analysis and fluorescence spectrum. The title compound crystallizes in triclinic, space group P with a = 11.611（3）, b = 15.610（5）, c = 15.624（7） , α = 113.942（6）, β = 104.520（6）, γ = 104.230（4）°, V = 2304.1（14） 3, C60H77Ag6N22O4.5S6, Mr = 2018.02, Dc = 1.454 g/cm3, μ（MoKα） = 1.435 mm-1, F（000） = 1005, Z = 1, the final R = 0.0468 and wR = 0.1474 for 6608 observed reflections （I 2σ（I））. In the structure, the S atom of the ligand L2 （L2 = benzaldehyde thiosemicarbazone） served as a triply bridged chelator to connect the six silver atoms into a Ag6L26 cluster. The luminescence property of compound 2 was investigated at room temperature.

Synthesis and Structure of Propionate-bridged Mixed-metal Cluster Compound: MoW_2O_2 (O_2CC_2H_5)_6 (H_2O)_3 ZnBr_4·4H_2O

The heterotrinuclear cluster compound [MoW_2O_2 (O_2CC_2H_5 )_6-( H_2O)_3] ZnBr4·4H_2O was prepared by the redox reaction of Mo (CO)_6 with Na_2W_O4 in propionic anhydride. The crystal is monoclinic of space group P2/c with a =16. 334(4) , b= 9. 657(5) , c=19. 889(9) ,β= 139. 79 (5)°,V= 2026 (2) ￣3 , Z=2 , D_c=2. 30 g/cm￣3 μ(MoKa) =106. 6 cm￣(-1) ,F(000)=1176 ,final R=0. 065 and R_ω=0. 072 for 1964 reflections with I≥3σ(I). In the structure of cation [MoW_2O_2 (O_2CC_2H_5 )_6 (H_2O)_3]￣(2+) molybdenum and tungsten atoms are statistically disordered. Three metal atoms form an equilateral triangle with the distance of M-M being 2. 735.

An Interpenetrated Three-dimensional Framework Sodium Lanthanide Carboxylate Based on[Ho_4(μ_3-OH)_4]^(8+) Cluster

A novel sodium holmium carboxylate compound,namely Na 4 Ho 4 （μ 3-OH） 4 （1,4BDC） 6 ·6.25H 2 O （1,1,4-BDC=1,4-benzenedicarboxylate）,has been solvothermally synthesized and structurally characterized.The structure features a two-fold interpenetrated three-dimensional open-framework constructed by the [Ho 4 （μ 3-OH） 4 ] 8＋ clusters bridged by 1,4-BDC ligands.The Na ＋ ions and lattice water molecules are located in the channels.The structure is further stabilized by hydrogen-bonding and π-π stacking interactions.The thermal stability of the compound has been investigated via thermogravimetric analysis.