Ppn Reaction Research Articles

Triple Coincidence Beam Spin Asymmetry Measurements in Deeply Virtual Compton Scattering

The Generalized Parton Distributions (GPDs) provides hitherto the most complete information about the quark structure of hadron. GPDs are accessible through hard-exclusive reactions, among which Deeply Virtual Compton Scattering (DVCS) is the cleanest reaction. A dedicated DVCS experiment on Hydrogen (E00-110) ran in the Hall A at Jefferson Laboratory in Fall 2004. I present here Beam Spin Asymmetry (BSA) results for the ep → epγ reaction studied in the E00-110 experiment with fully exclusive triple coincidence H(e, e'γp ) detection. I present a re-calibration of the electromagnetic calorimeter used to detect the high energy photon. This calibration is necessary to account for the effects of pile-up. The results show a 1-sigma disagreement with the double coincidence H(e, e'γ )p results, I also presents a feasibility study for measurements of neutron GPDs via the 3→He (e, e'γ)ppn reaction on a polarized 3He target with JLab at 12 GeV. These measurements offer the prospect of a determination of all four GPDs.

Analyzing Powers It11 and T20 of Dp -> Ppn Reaction at 400 Mev Investigated at Nuclotron

One of the tools to study spin structure of short range correlations (SRCs) and three nucleon forces is the measurement of the polarization observables. Deuteron induced reactions at intermediate energies are investigated at Internal Target Station (ITS) of Nuclotron through the dp elastic and dp → ppn reactions. Analyzing powers iT11 and T20 analyzing powers of dp → ppn reaction at 400 MeV are presented.

Experimental investigation ofdp→ppnreaction at intermediate energies at Nuclotron

There are still discrepancies between theory and experimental data in the po- larisation observables of dp → ppnreaction in the low and intermediate energies, despite of significant process in the development of theoretical models which include three and more nucleon forces and relativistic effects. The data of dp → ppn reaction have been accumulated at 300, 400 and 500 MeV in the Nuclotron (Dubna, Russia) and partially processed for some kinematic configurations including few in which possible relativis- tic effects can appear. Kinematic simulation in the framework of ROOT and GEANT4 package have been performed before data processing. Part of the preliminary results are obtained in the form of energy deposit correlations of the two arms working in coinci- dence and few in the form of kinematic S curve.

Experimental data on the dp → ppn reaction at the deuteron energy of 300–500MeV obtained at ITS at Nuclotron

The experiment on dp non-mesonic breakup at Internal Target Station at Nuclotron is presented. Recent results on the study of the dp-breakup reaction with 300–500[Formula: see text]MeV unpolarized deuteron beam at Internal Target Station at Nuclotron are discussed. Selection procedure of useful events for the [Formula: see text] reaction with the registration of two protons is shown. Further scientific program with polarized and unpolarized deuterons is discussed.

Synthesis of Au(I) Trifluoromethyl Complexes. Oxidation to Au(III) and Reductive Elimination of Halotrifluoromethanes

Au(I) trifluoromethyl complexes [Au(CF3)L] (L = N-heterocyclic carbene (NHC), isonitrile, phosphine, P(OMe)3) and [Au2(CF3)2(μ-dppe)] are prepared by reaction of [Au(X)L] (X = Cl, I) or [Au2Cl2(μ-dppe)], respectively, with AgF and Me3SiCF3. The analogous reaction of PPN[Au(C6F5)Cl] (PPN+ = [Ph3PNPPh3]+) gives a mixture of complexes of the type PPN[Au(CF3)x(C6F5)2–x] (x = 0, 1, 2). Single crystals of the new complex PPN[Au(CF3)(C6F5)] are obtained by liquid diffusion from this mixture, and its crystal structure was determined by X-ray diffraction. Acyclic diaminocarbene complexes [Au(CF3){C(NEt2)(NHR)}] (R = tBu, 2,6-dimethylphenyl) are obtained by reaction of [Au(CF3)(CNR)] with NHEt2. Oxidation of the NHC complex [Au(CF3)(IPr)] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with PhICl2, Br2, I2 or ICl affords [Au(CF3)(X)(Y)(IPr)] (X = Y = Cl, Br I; X = Cl, Y = I). The dicloro, dibromo, and chloro(iodo) complexes are stable in solution in the dark. In contrast, the diiodo complex is unstable and decomposes to [AuI(IPr)] and ICF3. Under photoirradiation, complexes [Au(CF3)(X)(Y)(IPr)] undergo reductive elimination to give YCF3 and [AuX(IPr)] (X = Y = Cl, Br; X = Cl, Y = I).

Few-body Studies at Nuclotron-JINR

Recent results on the deuteron analyzing powers in dp- elastic scattering obtained at Nuclotron (JINR, Dubna) are compared with the calculations performed within relativistic multiple scattering model. The data demonstrate strong deviation form the predictions at large angles in the cms. The preliminary data on the energy dependence of the cross section in the dp → ppn reaction at 150–250 MeV/nucleon for different configurations and dp elastic scattering up to 1 GeV obtained at internal target station at Nuclotron are reported. The prospects of the further few-body studies at JINR are discussed.

NUCLEON RESONANCES FROM DYNAMICAL COUPLED CHANNEL APPROACH OF MESON PRODUCTION REACTIONS

Properties of the nucleon resonances are investigated within a coupled channel model of πN, γN → πN, ηN, KΛ, KΣ and ππN reactions. The pole positions and the residues of the nucleon resonances are extracted by using the analytic continuation of the scattering amplitudes.

Experiment on the Study of the [formula omitted] Reaction at 300–500 Mev of the Deuteron Energy at ITS at Nuclotron

The experiment on dp non-mesonic breakup at Internal Target Station at Nuclotron-M is presented. The first results on the study of the dp-breakup reaction with 300-500 MeV unpolarized deuteron beam are discussed. Selection procedure of useful events for the dp→ppn reaction with the registration of two protons is shown.

The neutron-proton charge-exchange amplitudes measured in the dp → ppn reaction

The unpolarised differential cross section and the two deuteron tensor analysing powers A_{xx} and A_{yy} of the pol{d}p -> (pp)n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27 GeV, data were obtained for small momentum transfers to a (pp) system with low excitation energy. The results at the three lower energies are consistent with impulse approximation predictions based upon the current knowledge of the neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far more uncertain, agreement requires a reduction in the overall double-spin-flip contribution, with an especially significant effect in the longitudinal direction. These conclusions are supported by measurements of the deuteron-proton spin-correlation parameters C_{x,x} and C_{y,y} that were carried out in the pol{d}pol{p} -> (pp)n reaction at 1.2 and 2.27GeV. The values obtained for the proton analysing power also suggest the need for a radical re-evaluation of the neutron-proton elastic scattering amplitudes at the higher energy. It is therefore clear that such measurements can provide a valuable addition to the neutron-proton database in the charge-exchange region.

Diselenolate- and ditellurolate-carborane gold complexes

Gold complexes with selenolate and tellurolate carborane ligands [E2C2B10H10](2-) (E = Se, Te) have been synthesized by reaction of a freshly prepared solution of [1,2-(LiE)2C2B10H10] (E = Se, Te) with [AuClL] (L = PPh3, PPh2Me, PPh2py) in a 1 : 2 molar ratio or [Au2Cl2(P∼P)] [P∼P = dppf, 1,1'-bis(diphenylphosphano)ferrocene; dppe, 1,2-bis(diphenylphosphano)ethane; dppc, 1,2-bis(diphenylphosphano)-o-carborane] in a 1 : 1 molar ratio affording complexes [Au2(μ-1,2-E2C2B10H10)L2] or [Au2(μ-1,2-E2C2B10H10)(P∼P)], respectively. The gold(III) species PPN[Au(E2C2B10H10)2] (PPN = bis(triphenylphosphano)iminium) have been afforded by reaction of PPN[AuCl4] with [1,2-(LiE)2C2B10H10]. Complex [Au4(μ-1,2-Se2C2B10H10)2(μ-dppc)2] displays a tetranuclear structure, different from the dinuclear cyclic arrangement proposed for other complexes with diphosphanes of [Au2(μ-1,2-Se2C2B10H10)(P∼P)] stoichiometry.

The dp → ppn reaction as a method to study neutron-proton charge-exchange amplitudes

The differential cross section and deuteron analysing powers of the $$ \vec d $$ p → {pp}n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using a deuteron beam of energy 1170MeV, data were obtained for small momentum transfers to a {pp} system with low excitation energy. A good quantitative understanding of all the measured observables is provided by the impulse approximation using known neutron-proton amplitudes. The proof of principle achieved here for the method suggests that measurements at higher energies will provide useful information in regions where the existing np database is far less reliable.

Tungsten complexes of aromatic and aliphatic thioaldehydes

Reaction of PPN[W(CO) 3(R 2PC 2H 4PR 2)(SH)] (PPN=Ph 3PNPPh 3; R=Me, 1; R=Ph, 2) with aromatic aldehydes in the presence of trifluoroacetic acid gave tungsten complexes of thiobenzaldehydes mer-[W(CO) 3(R 2PC 2H 4PR 2)(η 2-SCHR ′)] (R=Me, 3a– 3f; R=Ph, 4a– 4e) in high yields. Analogous complexes of aliphatic thioaldehydes mer-[W(CO) 3(Me 2PC 2H 4PMe 2)(η 2-SCHR ′)] ( 3g– 3l) could only be obtained from the highly electron-rich thiolate complex 1. The structure of 3i (R ′= i-Bu) was determined by X-ray crystallography. In solution the complexes 3 and 4 are in equilibrium with small quantities of their isomers fac-[W(CO) 3(R 2PC 2H 4PR 2)(η 2-SCHR ′)]. Reaction of complexes 3 with dimethylsulfate followed by salt metathesis with NH 4PF 6 gave the alkylation products mer-[W(CO) 3(Me 2PC 2H 4PMe 2)(η 2-MeSCHR ′)]PF 6 ( 5a– 5l) as mixtures of E and Z isomers. The methylated thioformaldehyde complex mer-[W(CO) 3(Me 2PC 2H 4PMe 2)(η 2-MeSCH 2)]PF 6 ( 5m) was prepared similarly. Nucleophilic addition of hydride (from LiAlH 4) to 5 initially gave thioether complexes mer-[W(CO) 3(Me 2PC 2H 4PMe 2)(MeSCH 2R ′)] ( mer- 6) which rapidly isomerized to fac-[W(CO) 3(Me 2PC 2H 4PMe 2)(MeSCH 2R ′)] ( fac- 6).

Hybrid cluster-cages formed via cyanometalate condensation: Cs subset Co(4)Ru(6)S(2)(CN)(12), Co(4)Ru(9)S(6)(CN)(9), and Rh(4)Ru(9)S(6)(CN)(9) frameworks.

Condensation of cyanometalates and cluster building blocks leads to the formation of hybrid molecular cyanometalate cages. Specifically, the reaction of [Cs subset [CpCo(CN)(3)](4)[CpRu](3)] and [(cymene)(2)Ru(3)S(2)(NCMe)(3)]PF(6) produced [Cs subset [CpCo(CN)(3)](4)[(cymene)(2)Ru(3)S(2)][CpRu](3)](PF(6))(2), Cs subset Co(4)Ru(6)S(2)(2+). Single-crystal X-ray diffraction, NMR spectroscopy, and ESI-MS measurements show that Cs subset Co(4)Ru(6)S(2)(2+ ) consists of a Ru(4)Co(4)(CN)(12) box fused with a Ru(3)S(2) cluster via a common Ru atom. The reaction of PPN[CpCo(CN)(3)] and 0.75 equiv of [(cymene)(2)(MeCN)(3)Ru(3)S(2)](PF(6))(2) in MeCN solution produced [[CpCo(CN)(3)](4)[(cymene)(2)Ru(3)S(2)](3)](PF(6))(2), Co(4)Ru(9)S(6)(2+). Crystallographic analysis, together with NMR and ESI-MS measurements, shows that Co(4)Ru(9)S(6)(2+ ) consists of a Ru(3)Co(4)(CN)(9) "defect box" core, wherein each Ru is fused to a Ru(3)S(2) clusters. The analogous condensation using [CpRh(CN)(3)](-) in place of [CpCo(CN)(3)](-) produced the related cluster-cage Rh(4)Ru(9)S(6)(2+). Electrochemical analyses of both Co(4)Ru(9)S(6)(2+) and Rh(4)Ru(9)S(6)(2+) can be rationalized in the context of reduction at the cluster and the Co(III) subunits, the latter being affected by the presence of alkali metal cations.

New Ylide−, Alkynyl−, and Mixed Alkynyl/Ylide−Gold(I) Complexes

Reactions of AuCl(tht) (tht = tetrahydrothiophene) with various ylides in equimolar amounts give the complexes [AuCl(ylide)]Xn (n = 0, ylide = C(PPh3)2 (1a), 4-MeC6H4SO2CHPPh3 (1b); n = 1, X = TfO, ylide = [HC(PPh3)2]+ (2)) and [(AuCl)2{μ-C(PPh3)2}] (3) when using a 2:1 molar ratio. The complex 1a reacts (i) with Tl(acac) to give [Au(acac){C(PPh3)2}] (4) and (ii) with terminal alkynes (with or without added Et3N) to give [HC(PPh3)2][Au(C⋮CC6H4R-4)Cl] (R = H (5a), CN (5b), OMe (5c), NO2 (5d)) instead of the desired complexes [Au(C⋮CC6H4R-4){C{PPh3}2}]. These complexes (R = H (6a), CN (6b), OMe (6c), NO2 (6d), C⋮CPh (6e)) were prepared by the reaction of [Au(acac){C(PPh3)2}] (4) with a large excess of alkynes (ca. 1:25−30). Complex 1b reacts with terminal alkynes in the presence of Et3N differently from 1a, giving the complexes [Au(C⋮CC6H4R-4){CH(PPh3){S(O)2C6H4Me-4}}] (R = H (7a), NC (7b), OMe (7c), NO2 (7d), C⋮CPh (7e)). The reaction of PPN[Au(acac)2] with the phosphonium salt [H2C(PPh3)2](TfO)2 or [4-MeC...

Argento– aurophilic bonding in organosulfur complexes. The molecular and electronic structures of the heterobimetallic complex AgAu(MTP) 2

The heterobimetallic complex AgAu(MTP) 2, ( 1), was obtained from the reaction of PPN[Au(MTP) 2] with AgNO 3 (MTP=diphenylmethylenethiophosphinate; PPN=bis(triphenyl-phosphoranylidene)ammonium). Compound 1 was found to be isomorphous with but not isostructural to the previously reported compounds Au 2(MTP) 2, ( 2) and Ag 2(MTP) 2, ( 3). Surprisingly, 1 has a very short intramolecular AgAu distance (2.912 Å), which is much shorter than the intramolecular metal–metal distances in 2 and 3 (∼3.0 Å in both). The three compounds form extended one-dimensional chain structures in the solid state. The intermolecular interactions in 1 were found to be AgAu interactions (3.635 Å), as opposed to AuAu and AgAg interactions. Density-functional theory (DFT) calculations were used to study the stability of the geometrical isomers with different coordination modes of the MTP ligand in models of 1– 3. Isomers with AgC bonds were found much higher in energy than those with AuC bonds, which explains the stability of 1 and 2, which have AuC bonds, relative to 3, which has two AgC bonds. Dilute solutions of the three compounds showed virtually identical absorption spectra in which the lowest-energy band is due to a π–π* intraligand transition. The electronic spectra for concentrated solutions and the solid state show lower energy bands due to intermolecular interactions. The relative energies of the absorption edge followed the order Au 2≪AgAu<Ag 2. DFT calculations demonstrate that monomer models cannot describe this trend. However, DFT calculations for dimer and trimer models of the three compounds give excellent agreement with the experimental results, as the HOMO–LUMO gap follows the same order as the absorption edge. The importance of intermolecular metal–metal interactions is further manifested by the presence of emission bands in the visible region for the three compounds. Crystal data for AgAu(CH 2P(S)Ph 2) 2: monoclinic, space group C2/ c; Z=8; a=24.384(2) Å; b=6.5472(6) Å; c=16.4884(18) Å; β=113.356(5)°.

Synthesis, structure, DFT calculations, and full vibrational analysis of the prototypical thioformaldehyde complex mer-[W(CO)3(Me2PC2H4PMe2)(η2-SCH2)

Reaction of PPN[W(CO)3(dmpe)(SH)] 2 (PPN = Ph3PNPPh3, dmpe = Me2PC2H4PMe2) with aqueous formaldehyde in the presence of trifluoroacetic acid gives the thioformaldehyde complex mer-[W(CO)3(Me2PC2H4PMe2)(η2-SCH2)] 3 in almost quantitative yield. The isotopomer mer-[W(CO)3(Me2PC2H4PMe2)(η2-SCD2)] 3-D22 was obtained analogously. 3 has a slightly distorted pentagonal-bipyramidal structure with one carbonyl group, two P atoms and the C and S atoms of the thioformaldehyde ligand spanning the pentagonal plane. In solution, 3 is in equilibrium with fac-[W(CO)3(Me2PC2H4PMe2)(η2-SCH2)] 4. The structures and energies of 3 and 4 and their rotamers 3′ and 4′ were calculated by DFT methods leading to a very good agreement with experimental data. FT-IR and FT-Raman spectra of 3 and 3-D22 were recorded and assigned with the aid of DFT calculations. Calculated vibrational amplitudes emphasize the extensive mixing of modes, particularly in the low-wavenumber region. The HOMO of 3 can approximately be described as a lone-pair at sulfur and is 0.38 eV higher in energy than that of isomer 4. The LUMOs of both isomers are highly delocalized with that of 4 being 0.45 eV lower in energy. On this basis it is expected that electrophiles will add preferentially at the sulfur atom of 3 while nucleophiles if at all will add to the thiocarbonyl carbon of 4.

Production of isoscalar pion pairs in the [formula omitted] reaction near threshold

The production near threshold of isoscalar pion pairs in the pd→ 3 He(ππ) 0 reaction is estimated in a two-step model which successfully describes the production of η, ω and η′ mesons. A virtual pion beam, generated through an NN→ dπ reaction on one of the nucleons in the deuteron, produces a second pion via a πN→ ππN reaction on the other nucleon. Using the same scale factor as for heavy meson production, the model reproduces the total π 0 π 0 production rate determined at an excess energy of 37 MeV. There are some indications in the data for a suppression of events with low ππ masses, as in the π − p→ π 0 π 0 n reaction, and this is confirmed within the model. The model suggests that a significant fraction of the charged pion production in the pd→ 3 Heπ +π − reaction at Q=70 MeV might be associated with isoscalar pion pairs, though this does not explain the strong dependence observed on the π + π − relative momentum angle.

Determination of the ππ scattering lengths from data on πN → ππN reactions by the method of Roy equations

Fitted phase-shift curves from the threshold to the dipion mass, which is equal to 1 GeV, are constructed on the basis of all available experimental values of the S-and P-wave phase shifts for five charged channels of pion-pion scattering. The resulting phase-shift curves are introduced in the Roy equations in order to obtain the subtraction constants λ (s). By using these subtraction-constant values as functions of the dipion mass, the S 0-and S 2-wave pion-pion scattering lengths are found to be a 0 0 = (0.240 ± 0.023)m π −1 and a 0 2 = (−0.034 ± 0.013)m π −1 . A strong correlation of the S-wave scattering lengths is demonstrated.

A model for πΔ electroproduction on the proton

We have extended a model for the γN→ ππN reaction to virtual photons and selected the diagrams which have a Δ in the final state. With this model we have evaluated cross sections for the virtual photon cross section as a function of Q 2 for different energies. The agreement found with the γ v p→ Δ 0 π + and γ v p→ Δ ++ π − reactions is good. The sensitivity of the results to NΔ transition form factors is also studied. The present reaction, selecting a particular final state, is an extra test for models of the γ v N→ ππN amplitude. The experimental measurement of the different isospin channels for this reaction are encouraged as a means to unravel the dynamics of the two pions photoproduction processes.

Deactivation of a [PPN][Rh(CO)4]-based catalytic system [PPN+ = (PPh3)2N+]. The first decomposition reaction of PPN+ and the formation of [Rh10P(CO)22]3−

Decomposition of [PPN][Rh(CO)4] [PPN+ = (PPh3)2N+] at 200 °C under CO pressure affords [Rh10P(CO)22]3−, featuring the first decomposition reaction of PPN+ and explaining the reason for the deactivation of [PPN][Rh(CO)4]-based catalytic systems.