Fast emission ofα-particles in deep-inelastic36Ar+197Au collisions

Angular and energy correlations betweenα-particles and deep-inelastic projectile-like fragments were measured for the system³⁶Ar+¹⁹⁷Au atE _Lab=380 MeV. At most half of the coincident events can be attributed to statistical emission ofα-particles from the fully accelerated projectile-like fragments. The remainder of the events may be due to direct emission during the first 10^?22 s of the scattering process and to preequilibrium processes taking place within some 10^?21 s.     

Structures in the excitation functions for compound reactions in the12C+14C system

Excitation functions for the elastic scattering of¹²C on¹⁴C and the reactions¹⁴C(¹²C, α)²²Ne,¹⁴C(¹²C,t)²³Na and¹⁴C(¹²C,d)²⁴Na have been measured in the vicinity of the Coulombbarrier. Strong fluctuations of the differential cross sections as a function of incident energy are observed in the α-particle, triton and deuteron channels. The total yield in the three different channels shows correlated structures at energiesE _c.m.=6.8, 7.2 and 8.3 MeV. This phenomenon is similar to the structures observed in the¹²C+¹²C reactions and indicates the possible presence of resonances in the entrance channel.     

Interfering proton and neutron transfer in the reaction C(N, N)C

Elastic scattering and one-nucleon transfer reactions induced by ¹⁶O have been investigated in the energy region 45–60 MeV on targets of ²⁶Mg, ²⁷Al, ³⁰Si and ⁴⁸Ca. Angular distributions were measured in the angular range 4°–40°. Optical model parameters were derived from the elastic scattering data and the transfer reaction data were analysed using both no-recoil and full-recoil DWBA codes. In the case of proton transfer reactions on ⁴⁸Ca, good agreement was obtained between the data and the DWBA calculations while the data for the lighter targets could not be satisfactorily reproduced. The oscillatory pattern of the angular distributions is discussed in terms of the three-parameter model of Kahana, and it is found that the model qualitatively explains the observed transition from smooth to oscillatory angular distributions.     

Light particle emission in quasi-elastic heavy-ion reactions

Angular and energy correlations betweenα-particles and quasi-elastic projectile-like heavy ions have been measured for³⁶Ar+¹⁹⁷Au collisions atE _LAB=380MeV. The majority of the observed coincident events can be understood in terms of a statistical emission process whereas only a small fraction of the events, mainly at forward angles, can be attributed to a direct process.     

Pairing effects in quasi-elastic neutron transfer between Tin isotopes

The transfer of neutrons between low-lying states of Tin isotopes has been measured in the reaction¹²⁰Sn→¹¹²Sn at energies below the Coulomb barrier. The transfer probabilities are deduced as function of the classical minimum distance from transfer and scattering cross sections at different angles and two energies. At the smallest distances very large transfer probabilities,p _t =0.5, are observed for one- and two-neutron transfer. The two-neutron transfer is significantly enhanced as compared to a successive independent single-nucleon transfer. The definition of enhancement is discussed.     

Elastic scattering of15N on19F,19F on18O and19F on16O at low energies and elastic transfer

The reduced matrix elements for the ground state transitions to the first 2⁺, 3^? and 4⁺ states in¹⁴⁰Ce and¹⁴Ce were determined by DWBA analysis. In the giant resonance region of Ce, La and Pr three broad resonances at excitation energies of 9, 12 and 15 MeV have been found. They are interpreted asM1,E2 andE1 giant resonances. For Ce the total widths are (2.2±0.4) MeV (M1) and (2.8±0.3) MeV (E2) and the groundstate radiative widths (90±45) eV (M1), (100±30) eV (E2) and (5±1) · 10⁴ eV (E1).     

Determination of theQ-value dependence of charged particle emission in the40Ca+40Ca reaction at 10 MeV/nucleon

An iterative method for the determination of the charged particle loss as a function of the reactionQ-value is developped. The analysis is based on experimental data resulting from 400 MeV⁴⁰Ca+⁴⁰Ca collisions.Z distributions are obtained at different calculatedQ-values corrected for evaporation and show rather good agreement — in the strongly damped case — with the ones derived from the OVERLAID ALICE code. Mean numbers of evaporated particles exhibit a linear increase as a function of these correctedQ-values; this corresponds to the evolution from quasi-direct to fully relaxed reactions.     

Temperature Dependence of the Crystal Structure and EPR Spectrum of Bis(1,3,5-Trihydroxycyclohexane)copper(II) Tosylate. A Unified Interpretation Using a Model of Dynamic Vibronic Coupling

The crystal structure of bis(1,3,5-trihydroxycyclohexane)copper(II) tosylate is reported at temperatures of 293, 233, 188, 163, and 93 K, as are the structures of the Zn(II) and Ni(II) analogues at room temperature for comparison. The isomorphous compounds are triclinic, space group P&onemacr;, with one formula unit in the unit cell. The unit cell parameters of the Cu compound at 293 K are a = 6.456(5) ?, b = 9.505(3) ?, c = 12.544(3) ?, alpha = 76.57(2) degrees, beta = 87.48(4) degrees, gamma = 76.65(4) degrees. The centrosymmetric ZnO(6) and NiO(6) octahedra are tetragonally compressed with a slight orthorhombic distortion. The Cu(2+) polyhedra exhibit similar geometries, but with considerably larger deviations from a regular octahedron. Two of the three independent Cu-O bond lengths and two of the g-values change significantly as a function of temperature. A model of dynamic vibronic coupling is presented which explains both the EPR and structural data. Vibronic wave functions associated with a Jahn-Teller potential energy surface modified by an orthorhombic lattice "strain" are given. The temperature dependence of the structures is calculated from the nuclear parts and that of the g-values from the electronic parts of the wave functions. The temperature dependence of the structures and g-values is also interpreted using a simpler model involving an equilibrium between two forms of the complex which differ solely in their orientation in the crystal lattice, and the results of the two approaches are compared.     

Mechanism of neon-induced reactions studied between 7.5 and 20 MeV/nucleon: Inclusive cross sections

Light and projectile-like fragments as well as fission fragments have been observed from the ²⁰Ne + ¹⁹⁷Au system at 150, 220, 290 and 400 MeV beam energy. Inclusive cross sections are given, and characteristic parameters like the centroids and the widths of momentum, Z- and A-distributions were derived. For comparison, some results of measurements on the ²²Ne + ¹⁹⁷Au and ^{20, 22}Ne + ⁵⁸Ni systems are included. The qualitative behaviour of the cross sections and the derived parameters show that with increasing bombarding energy the incomplete-fusion mechanism (massive transfer) and the sequential decay of projectile transfer residues (sequential break-up) appear in addition to the complete-fusion and ordinary transfer reactions predominant at the lowest bombarding energies. Other mechanisms do not contribute significantly in the energy range up to 20 $\text{MeV}\text{nucleon}$.     

Out-of-plane correlations of α-particles and heavy ions in the reaction of 373 MeV32S with gold

Out-of-plane correlations between α-particles and projectile-like heavy ions have been measured for the system³²S+¹⁹⁷Au at E_LAB=373 MeV. The angular widths of the correlations range from 24° to 40° (FWHM) depending on theZ of the heavy ion. In the framework of a model calculation these widths are shown to be very sensitive to the outof-plane momentum of the α-particle at emission. It is concluded that only little heating of the reaction partners occurs prior to α-particle emission.