The dependence of fission time-scales on fragment mass asymmetry in the 20Ne+165Ho reaction at 50A MeV

The pre-scission and post-scission multiplicities of alpha particles were determined in coincidence with fission fragments for four windows of exit channel mass asymmetry in the reaction ²⁰Ne+¹⁶⁵Ho at 50A MeV. The technique used employed a kinematic analysis of the energy spectra of alpha particles as a function of the emission angle with respect to the fission axis. Using a procedure of fitting the experimental energy spectra with those resulting from a Monte Carlo simulation program, the total multiplicity of alpha particles was separated into pre-scission and post-scission components. Using the pre-scission and post-scission multiplicities, neutron multiplicity measurements and other empirical observations, both the initial excitation energy and the excitation energy at scission of the compound nucleus were determined. The pre-scission times in the de-excitation of a highly excited ¹⁷⁸W compound nucleus with initial excition energy of 570 MeV were evaluated using statistical model calculations. Only a small decrease in scission time was derived for the most asymmetric events studied. The possible contribution of very damped deep inelastic processes is discussed.     

DWBA and CCBA analysis of selected transitions in the C(d,τ) B reaction at Ed = 80 MeV

Angular distribution of the reaction ¹²C(d,τ) ¹¹B leading to the 3/2⁻ ground state and the 4.44 MeV excited (5/2⁻ state ¹¹B have measured at E_d = 80 MeV up to about 70° and 40°, respectively. The inclusion of second-order processes in the framework of CCBA calculations gives a good reproduction of the 3/2⁻ as well as of the DWBA forbidden 3/2⁻ angular distribution. The strong dependence of the cross section on the sign of the deformation supports a positive β₂ value for ¹¹B.     

Density, viscosity and ultrasonic velocity studies of aqueous solutions of sodium acetate at different temperatures

The densities and viscosities of aqueous solutions of sodium acetate have been measured at 298.15, 303.15, 308.15 and 313.15 K and at atmospheric pressure. The molality range has been studied between 6.09 × 10^− 2 to 7.314 × 10^− 1 mol kg^− 1. The experimental values of density have been used to calculate apparent molar volume, partial molar volume, solute–solute interaction parameter, and Hepler's constant. The viscosity data have been analyzed with Jone–Dole equation. Furthermore, ultrasonic velocity measurements of aqueous solutions of sodium acetate have been made at 298.15 and 308.15 K and at atmospheric pressure. From experimental values of ultrasonic velocity, apparent molar isentropic compressibility and limiting apparent molar isentropic compressibility have been calculated. All the parameters calculated from density, viscosity, and ultrasonic velocity indicate that the sodium acetate is water structure maker.     

Electro-pion production on O to bou nd states of the residual nuclei

Differential cross sections for the reactions 16O(γ, π−π+−)16F16F to the sum of the four lowest lying states in 16F and 16N have been measured as a function of angle for pions with a kinetic energy of 30 MeV. The extracted ratios R = σ(γ, π−)/σ(γ, π+), the first ones to discrete final states as a function of angle, are in fair agreement with results obtained for the nucleon. For positive pions the energy dependence of the cross section has been measured at the angles of 45° and 90°. Distorted wave impulse approximation calculations fail to describe the energy dependence.     

Studies on recoil proton tracks in NTA films with the T(d,n)He reaction

Recoil proton tracks in nuclear emulsion are counted by scanning them using strip, square or circular field of view of optical microscope. In this paper, the overestimate due to the edge effects in counting recoil proton tracks at different neutron energies produced from the T(d,n)⁴He reaction has been determined by measuring the true track density in NTA film. The overestimate has also been calculated using the measured value of the mean projected track length (L) in the film. The percentage of measured overestimates has been compared with those obtained by calculation and the results agree reasonably well. Fading effect in NTA film has been studied and found to be 22% more in the summer than in the winter season. A great reduction in fading rate could be achieved if the films are desiccated and sealed in highly pure dry nitrogen maintained at an over-pressure of 1000 Pa to reduce water vapour ingress. After the edge effect correction, the sensitivity of NTA film has been calculated from (1.72±0.08)×10⁻³ tracksn⁻¹ to (1.97±0.16)×10⁻³ tracksn⁻¹ in the neutron energy ranges from 15.91 to 18.88 MeV. The response was found to be from 0.24±0.02 trackscm⁻² permSv to 0.26±0.01 trackscm⁻² permSv in the same energy range.     

Search for narrow NNπ resonances in exclusive pp→ppππ measurements

Narrow structures in the range of a few MeV have been searched for in ppπ⁺ and ppπ⁻ invariant mass spectra (M_ppπ⁺ and M_ppπ⁻) obtained from exclusive measurements of the pp→ppπ⁺π⁻ reaction at T_p=725,750 and 775 MeV using the PROMICE/WASA detector at CELSIUS. The selected reaction is particularly well suited for the search for dibaryon resonances decoupled from NN and/or NΔ. In the mass range 2020 MeV/c²<m_dibaryon<2085 MeV/c² no narrow structures could be identified on the 3σ level of statistical significance neither in M_ppπ⁻ nor in M_ppπ⁺ giving an upper limit (95% C.L.) for dibaryon production in this reaction of σ<20 nb.     

Intermediate energy proton scattering and nuclear transition densities in nickel isotopes

Using the high-resolution spectrometer SPES-I, the angular distribution of 1.047 GeV protons scattered from ⁵⁸Ni, ⁶⁰Ni, ⁶²Ni, ⁶⁴Ni have been measured in the angular range 4–18°, up to 4.8 MeV excitation energy. The data are analyzed within the framework of Glauber multiple scattering theory using a spin-dependent NN scattering amplitude. The parameters of the neutron density distributions have been determined by a χ² analysis of elastic scattering. The inelastic data corresponding to the first 2⁺ and 3⁻ states are analyzed with the collective model and an attempt has been made to extract information about the corresponding neutron transition densities.     

Spectroscopy of C

The ¹⁴C(t, p)¹⁶C reaction locates five new states in ¹⁶C, at excitation energies of 3120 ± 15, 3983 ± 10, 4136 ± 10 and 6109 ± 15 keV, in addition to the g.s. and 1.76 MeV states. The 3.02 and 3.98 MeV states appear to be the second 0⁺ and 2⁺ 2p-2h states, respectively. The 4.14 MeV state has J^π = 4⁺ and the 6.11 MeV state has J^π = 2⁺, 3⁻, or 4⁺.     

New isomeric states in Fr and At

Alpha spectroscopic data from the decay chain ²¹⁸Fr → ²¹⁴At → ²¹⁰Bi have been obtained. Previously unobserved isomeric states were found in both ²¹⁸Fr and ²¹⁴At. The half-life of the ground state of ²¹⁸Fr was measured to be 1.3^+0.5 _−0.4 ms. The half-life of the new isomeric state in ²¹⁸Fr was determined to be 22.0±0.5 ms and its decay was found to be very complex with no fewer than 20 -groups varying in energy between 6837 keV and 7952 keV. Two long-lived states in ²¹⁴At with half-lives of 558±10 ns and 760±15 ns, respectively, were found to be strongly populated in the decay of ^218mFr. These two states are proposed to be a 1⁻ ground state and a 9⁻ isomeric state arising from the coupling between the unpaired h_9/2 proton and g_9/2 neutron.     

The Bi(d,γ)Po reaction

The yield of the ²⁰⁹Bi(d, γ)^211g.s.Po and ^211mPo (T_1/2 = 25.2s) reaction was measured for deuteron energies E_d = 8–11.5 MeV. The reaction was identified by the -activities of the Po isotope. At E_d = 10.43 MeV, the (d, γ) cross section for the population of the ground state of ²¹¹Po is σ_g.s. = 16 ± 3 μb, the ratio relative to the cross section for the metastable state is σ_g.s./σ_m = 25.4 ± 0.9. These values and the yield curves were compared with calculations using a simple model for the population of the two states. In the excitation region E* = 15–19 MeV, the branching ratio of γ- to particle emission is nearly constant and has a value of about 0.4 × 10⁻⁴.     

Search for a light neutral particle in the decay of the 3.68 MeV state in C

A search is made for a short lived neutral particle, ø, in the decay of the 3.68 MeV (3/2^-) state in ¹³C. No evidence for such a particle with a rest mass in the region of 1.7–2.0 MeV/c² is found with a limit on the branching ratio Γ _ø/Γ_γ7×10 ⁻⁵. An upper limit of 10⁻⁶ is placed for the coupling of such a particle to proton/neutron.     

Spin alignment in resonant C+O inelastic scattering

The spin alignment of the 3⁻ state (6.13 MeV) of ¹⁶O from inelastic scattering of ¹²C+¹⁶O has been measured in the energy region of known resonances around E_cm=20 MeV. The result, that the population of the m=±3 magnetic substates is enhanced on four resonances at 19.7, 20.5, 22.0 and 22.6 MeV, indicates the dominance of the aligned configuration on these resonances.     

Spectrophotometric microdetermination of phenylephrine hydrochloride in pure and in pharmaceutical formulations using haematoxylin

A simple, rapid, selective and sensitive method for the micro amount determination of phenylephrine hydrochloride either in pure form (raw material) or in pharmaceutical formulations is described. The method is based on the development of violet colour charge transfer complex with haematoxylin in alkaline medium with 10 min after heating at 65 °C. The wavelength and maximum absorption range was found in the range from 640 to 620 nm. Molar absorptivity and Sandell sensitivity were found to be 2.38 × 10⁴ L mol^− 1 cm^− 1 and 8.6 ng cm^− 2 respectively. A linear correlation was found between absorbance (at the λ_max) and concentration. The resulting colour is stable for more than 10 h. Results of the analyses of pure drug and dosage forms by the proposed method are in good agreement with those of the official BP 1998 procedure.     

Cross section of the charged current reaction C(ve, e)Ng.s.

The charged current nuclear transition ¹²C(v_e, e⁻)¹²N_g.s. has been observed in the KARMEN experiment. The flux average cross section for v_e from μ⁺ decay at rest is determined to be σ = [8.1±0.9(stat.)±0.75 (syst.)]×10⁻⁴²cm². For the first time also the energy dependence of the cross section has been measured for neutrino energies up to 50 MeV.     

βγ(CP) correlation measurements and anti-analogue structure in the decay of Ca

β-γ(CP) correlation measurements have been carried out on the sequence in the decay of the ground state of ⁴⁹Ca to the (presumed) anti-analogue state at 3.105 MeV excitation in ⁴⁹Sc. An asymmetry parameter of A = −0.132 ± 0.017 was obtained, making any spin-parity assignment other than very unlikely for the 3.105 MeV state. The deduced Fermi matrix element for the decay is |M_{v| = |1.4 ± 9.7| × 10⁻³}, which leads to an isospin impurity ( ) corresponding to the mixing of the analogue state (at 11.6 MeV) and the 3.105 MeV state of ||² 1.6 × 10⁻⁵. This leads in turn to an effective Coulomb matrix element of |H_c| = |3.9 ± 27.4| keV, a low value compared to the value of 100 keV obtained from a theoretical estimate based on simple shell-model wave functions for the single-particle states involved.     

The lifetime of the 3.74 MeV (3) state of Ca

The mean life of the 3.74 MeV (3⁻) excited state of ⁴⁰Ca has been directly measured by a particle-gamma delayed coincidence technique. A mean life τ = 59 ± 5 ps was obtained, corresponding to a transition strength B(E3) = 31 ± 3 W.u.     

Emission of intermediate mass fragments in the heavy ion interaction of (14.0 MeV/u) Pb+Au

We have studied the heavy ion interactions of (14.0 MeV/u) Pb + Au using two threshold detectors, mica and CN-85. A thin layer of Au was deposited on each of the three mica and two CN-85 detector pieces. These target-detector assemblies were exposed to a beam of 14.0 MeV/u Pb ions having the fluence of 1.5×10⁶ cm² at GSI, Darmstadt, Germany. After removing the target material and etching the samples in appropriate etchants, we scanned 32.29 cm² and 24.97 cm² area of mica and CN-85, respectively. Based on the observed number of events of various multiplicities, we have determined the total as well as partial experimental reaction cross-sections. It is shown that a significant number of intermediate mass fragments are emitted alongwith the heavy fragments in the present reaction.     

Polarisation circulaire du rayonnement gamma de Sb, Cs et Ag

The βγ circular polarization correlation of the 3⁻(β⁻ 621 keV)3⁻(γ 1692)2⁺ cascade in ¹²⁴Sb, the 4⁺(β⁻ 662)4⁺ (γ 796)2⁺ (γ 605)0⁺ in ^13Z4Cs and the 6⁺(β⁻529)6⁺ (γ 937)4⁺ (γ 885)2⁺ (γ 658)0⁺ in ^110mAg have been studied by using a Compton effect polarimeter. The measured asymmetry parameters are 0.172±0.004, −0.0702 ±0.0024 and 0.0549±0.0013 respectively.     

Enhanced performances of ZnO-TFT by improving surface properties of channel layer

Top-contact thin film transistors with ZnO as the channel layer and thermally grown SiO₂ as the gate dielectric were fabricated by using rf sputtering. The performances of ZnO-TFTs with different thicknesses of the active layer were investigated and the optimized condition was obtained. With the active layer thickness from 25 to 70 nm, the leakage current of devices increased from 10⁻¹⁰ to 10⁻⁸ A, and the on/off ratio decreased from 1.2×10⁷ to 2×10⁴. Atomic force microscope research indicated that with the thickness increased, the surface morphology of the active layer improved noticeably at first and then deteriorated. The 25-nm-thick ZnO TFT had the best surface morphology, and showed the best performance with a field effect mobility of 5.1 cm²/V S, on/off ratio of 1.2×10⁷ and threshold voltage of 20 V. This indicates that the surface properties of the channel layer have crucial affects on the performances of ZnO-TFTs.