On the excitation of isovector dipole strength by inelastic proton scattering in the giant resonance region in light nuclei

A detailed comparison between inelastic α and p scattering in the giant resonance region of ^{24, 26}Mg, ²⁸Si and ⁴⁰Ca shows that there is no evidence for ΔT = 1, E1 excitation in the (p, p′) spectra. This is consistent with DWBA calculations using a recently obtained isovector interaction potential.     

Influence of the shape of the exciting laser pulse on fluorescence saturation in the quantitative analysis of dissolved trace organic substances

Theoretical investigations of the influence of the exciting laser pulse shape on fluorescence saturation in the quantitative analysis of a single-component fluorescing solution, when the Raman signal of the solvent is usedas a reference, are carried out. A quantity α is introduced, responsible for the influence of laser pulse shape on the precision of the analysis. The dependences of α on the exciting radiation photon flux density I_m in the range I_m = 10²² ? 10²⁸ photons/cm²?s and on the duration of the exciting pulses τ_p in the range τ_p = 0.6 ? 60 ns are computed for different pulse shapes in the case of rhodamine 6G dissolved in water. Conditions when α is, in practice, independent of τ_p and of the pulse shape are found. A general analytical expression is found for α, which produces errors not greater than several percent when compared to the computed values of α. An experimental verification of the theoretical results in the case of a rectangular-shaped pulse in the spatial domain and a Gaussian-shaped pulse in the temporal domain is realized.     

Stepwise ionization of the 2,4-dioxybenzaldehyde and 3,4-dimethoxypropiophenone vapors

The processes of stepwise ionization of the 2,4-dioxybenzaldehyde and 3,4-dimethoxypropiophenone vapors by radiation in the range of wavelengths down to 266 nm were studied using total-current spectroscopy, mass spectrometry, and photoelectron spectroscopy. The process of two-step ionization and the resulting generation of molecular ions are dominant if the laser-radiation intensity amounts to ≈10⁶ W/cm². These molecular ions have appreciable (up to 1.8 eV) energy of vibrational excitation. As the laser-radiation intensity increases, progressively more pronounced fragmentation occurs owing to dissociation of molecular (and, possibly, fragmentation) ions as a result of absorption of at least a single additional photon. The processes leading to fragmentation of ions are suggested. It is found that the dissociation-ionization mechanism is important for the dimethoxypropiophenone. Dissociation with a breakage of the α bond in the carbonyl group with subsequent two-photon ionization of the fragments occurs when the S ₂(¹ A′) state of the ππ* type is excited.     

Two schemes ofη−η′-mixing

Proceeding from the expansion of composite operators in interpolating hadronic fields, the width of the decays η(η′)→γγ andJ/ψ→η(η′)γ have been calculated. Two mechanisms of pseudoscalar field mixing (“mass-mixing” and “current-mixing”) are considered. In the given schemes, the values of η?η′-mixing angle θ _p are, respectively, (?15.0±1.8)^o and (?19.7±2.2)^o.     

The role of the imaginary part in the microscopic description of (p,p′) scattering

A (p, p′) scattering experiment at E_p = 40 MeV was performed on the targets ⁹²Mo and ^{116, 120, 124}Sn. The addition of a simple collective imaginary from factor to the microscopic real form factor provides an important improvement in the agreement between calculated and experimental cross sections for the lowest 2⁺ and 3^? states. Results concerning the ΔT = 1 and ΔT = 0 contributions to the transitions are discussed.     

Level structure of 205Tl observed in (p,p′) and (p, α) reactions

A number of new levels in ²⁰⁵Tl have been observed in the ²⁰⁸Pb(p, α)²⁰⁵Tl and ²⁰⁵Tl(p, p′)²⁰⁵Tl reactions. The spectra observed in these reactions are very different from each other, and from spectra previously observed in the ²⁰⁶Pb(t, α)²⁰⁵Tl and ²⁰⁵Tl(γ,γ′)²⁰⁵Tl reactions. Values of G_L (reduced transition probability in single-particle units) have been deduced from the (p, p′) data; they are in fair agreement with the predictions of the intermediate-coupling model.     

Fine structure of analogue states in 45Sc

Differential cross sections were measured for ⁴⁴Ca(p, p′) and ⁴⁴Ca(p, p') at four angles between E_p = 1.5 and 3.0 MeV, with an overall energy resolution of about 325 eV. Spins, parities, total and partial widths were extracted for 429 resonances. Five analogue states were identified and fits to the fine structure were obtained for four of these analogues.     

Free-carrier absorption in p-type Pb0.79Sn0.21Te

Results are presented of the room-temperature absorption coefficient (α) of Pb_0.79Sn_0.21Te (p_77K = 2 × 10¹⁶-6 × 10¹⁷cm^-3) in wavelength (λ) range 6–15 μm. At long wavelengths α exhibits a λ² dependence, in agreement with the classical free-carrier absorption expression, and in this region α is proportional to carrier density.     

Photoionization and photoelectron angular distribution for H2

Photoionization of H₂(¹Σ_g⁺) in a vibrational υ″ and rotational N″ state into H₂⁺(²Σ_g⁺) in a vibrational υ′ and rotational N′ state is studied theoretically. The differential cross section, after summing over the final states, is expressed in the well-known simple form of $\text{(}\text{σ}{}_{\mathrm{T}}\text{4π}\text{)[1 + βP}{}_2\text{(}\text{cos}\text{θ)]}$. Parallel expressions are obtained for H₂⁺ in a specific υ′ state (in terms of σ(υ′) and β(υ′)) and for H₂⁺ in a rotational fine level υ′N′ (in terms of σ(υ′N′) and β(υ′N′)). Asymmetry parameters β, β(υ′) and β υ′N′), which are expressed in terms of Racah and Clebsch-Gordan coefficients and electronic transition moments, can be reduced approximately to 2 lineary polarized light and to -1 for unpolarized light. Using single-center electronic wave functions and including partial eaves l = 1, 3, and 5, σ(υ′) and β(υ′) are computed as a function of υ′ at 584 Å. The computed σ(υ′) divided by the Frank-Condon overlap, in agreement with experimental results, increases monotonically with υ′; σ_T and β are computed in the incident photon energy range of 600–4000 Å and the results compare favorably with previous calculations.     

Fluctuations in 88Sr(p,p0) and 90Zr(p,p′) in the energy region from 12 MeV TO 13 MeV

The low cross sections in the diffraction minima of elastic proton scattering at 12.5 MeV incident energy and far backward scattering angles for target nuclei with mass numbers A of about 90 were used to investigate compound nucleus effects in the framework of the statistical model. In the case of ⁹⁰Zr(p, p′) energy averaged T^< fluctuations are observed, while in the case of ⁸⁸Sr(p, p₀) resolved structures with a coherence width of Γ = 22 keV are found, which is assumed to be the coherence width Γ^> of overlapping T^> states.     

Observation of the second 4+ state in 28Si by means of proton inelastic scattering and analysis of the Kπ = 01+and 31− bands

High-resolution data from the ²⁸Si(p, p′) reaction have been obtained at E_p = 26.3 MeV. Separate cross sections for the 3₁^? and 4₂⁺ states at 6.879 and 6.889 MeV have been obtained. The strength of the 4₂⁺ state is much larger than reported in previous experimental papers. The 3₁^? state is well described in a coupled-channels calculation based on the rotation-vibration model.     

Excitation of high-spin unnatural parity states in 208Pb from the (p,p′) reaction at 135 MeV

Differential cross sections for the excitation of states at 6.42, 6.73 and 7.04 MeV in ²⁰⁸Pb by 135 MeV protons are reported. Both the excitation energies and the backward peaked angular distributions observed in this experiment and in a recent (e, e′) experiment strongly suggest that these states are predominantly one-particle-one-hole excitations with J^π = 12^?, 14^? and 12^?, respectively. The present (p, p′) data are interpreted using a distorted wave impluse approximation and the effect of configuration mixing between the two 12^? states is investigated.     

The magnetic two-centre problem: Nuclear fusion catalyzed by ultrastrong fields?

Employing the finite-element method (FEM), accurate potential energy curves for the ground state of the homonuclear system consisting of two (static) protons and one electron within a parallel homogeneous magnetic field are computed. The shrinking of the internuclear equilibrium separation with growing magnetic field strength is investigated under quantitative and qualitative aspects. In particular, we study the problem whether this leads to significantly enhanced nuclear fusion rates in the processes d (t, n) α and p (p, e ⁺ ν) d.     

Structure and reaction calculations in the RPA

The cross sections for the reaction²⁰⁷Pb (n, n′)²⁰⁷pb^* and the influence of continuum coupling on states in²⁰⁸Pb are discussed within the framework of the RPA.     

Defect structure of Cu-doped BaTiO3

Electrical conductivity σ and thermopower α were studied at temperature 1150–1350 K and in the P_O2 range between 2×10^-11-2×10⁴ Pa. Both σ and α data are well consistent, n- and p-type conductivity ranges were found at low and high P_O2 values, respectively. The power of P_O2 dependence for Cu-doped BaTiO₃ vary the oxide composition. This effect is discussed in term of the defect structure of BaTiO₃ and its solutions with CuO.     

Analyzing Power in Elastic Scattering of Polarized Protons from Neutron-rich Helium Isotopes

The vector analyzing power has been measured for the elastic scattering of neutron-rich ⁶He from polarized protons at 71 MeV/nucleon. Two approaches based on local one-body potentials were applied to investigate the spin-orbit interaction between a proton and a ⁶He nucleus. An optical model analysis revealed that the spin-orbit potential for ⁶He is characterized by a shallow and long-ranged shape compared with the global systematics of stable nuclei. A semi-microscopic analysis with a α + n + n cluster folding model suggests that the inclusion of realistic interaction between a proton and the α core is important in describing the p-⁶He elastic scattering.     

The 25Mg(p, γ)26Al and 25Mg(p,p′) resonances for Ep = 0.31–1.84 MeV

Thin target yield curves with good statistics have been measured for the ²⁵Mg(p, γ)²⁶Al and ²⁵Mg(p, p′)²⁵Mg reactions in the E_p = 310–1845 keV region. Altogether 76 resonances have been observed, of which 45 only in (p, γ), 30 in both (p, γ) and (p, p′), and one only in (p, p′). Several of these resonances had not been observed previously in either of the two reactions, and several of the previously observed resonances turned out to be doublets. All 39 ²⁵Mg(p, p₀)²⁵Mg resonances found previously in the E_p = 700–1845 keV region resonate in (p, γ) and many also in (p, p′). Resonance strengths have been derived relative to that of the E_p = 593 keV resonance.The analysis of weak (p, p₁) and (p, p₂) resonance yields has been supported by a calculation of the yields in the continuum (in between resonances) due to the Breit-Wigner tails of strong and broad resonances in the neighbourhood (with interference between resonances with the same J^π; T taken into account), and to Coulomb excitation.