[en] Excitation functions and differential recoil range distributions in the interaction of ¹⁶O with ⁷⁵As have been measured to investigate complete and incomplete fusion reactions. The measured cross sections were compared with theoretical calculations using the computer code ALICE-91. The results indicated predominant incomplete fusion processes in the production of near target products. This was further confirmed by recoil range distribution studies of the products at 104 MeV of beam energy. The relative contributions of complete and incomplete fusion channels are estimated from recoil range distribution measurements. (author)

[en] The excitation function for production of 262Bh in the odd-Z-projectile reaction 208Pb(55Mn,n) has been measured at three projectile energies using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. In total, 33 decay chains originating from 262Bh and 2 decay chains originating from 261Bh were observed. The measured decay properties are in good agreement with previous reports. The maximum cross section of 540 +180 - 150 pb is observed at a lab-frame center-of-target energy of 264.0 MeV and is more than fives times larger than that expected based on previously reported results for production of 262Bh in the analogous even-Z-projectile reaction 209Bi(54Cr,n). Our results indicate that the optimum beam energy in one-neutron-out heavy-ion fusion reactions can be estimated simply using the ''Optimum Energy Rule'' proposed by Swiatecki, Siwek-Wilczynska, and Wilczynski

[en] The selective excitation of a low frequency drift mode in the MaPLE (Magnetized Plasma Linear Experimental) device is reported. In the region there exists a parallel flow of electrons causing the drift modes to have a strong growth rate over a band of frequencies. However, the frequency selection for excitation is done in the experiment by driving a strong modulation of electron density with a frequency that is resonant in this region. The parallel velocity component of the excited m = 2 mode couples nonlinearly with the externally created density fluctuation to produce a parallel current fluctuation with twice the frequency. This selectively drives a second drift mode resonant in a nearby location. In this experiment the m = 4 drift mode is stable and hence not excited. Interestingly, this mode starts appearing as the modulation parameters cross a threshold value to drive parametric mode-mode coupling in the plasma. The excited mode satisfies the frequency and wave number matching conditions. A parametric mode-mode coupling of drift waves was reported before where the pump drift mode excites two lower frequency modes which are normally stable. In contrast, here it is demonstrated that the pump drift wave can parametrically excite the higher frequency drift mode with a substantial growth rate of the lower frequency

[en] To measure fusion excitation functions and the barrier distribution using recoil separator through Heavy Ion Recoil Analyzer (HIRA) at Inter University Accelerator Center (IUAC), New Delhi, India, a good quality, uniform and thin self supporting targets are preferable. Since the fabrication of such targets is very difficult, a considerable thin carbon foil as a backing is needed. Some trials of fabrication of carbon-backed targets were done with natural Ni. After optimizing the parameters, required isotopic targets (^61,62Ni) were fabricated

[en] A long-standing theoretical change is predictions of optimum incident systems, optimum incident energies, as well as those of maximum residue cross sections for synthesis of super-heavy elements (SHE). Theoretical predictions, however, have ambiguities stemming from two causes: unknown masses or shell correction energies (SCE) of SHE nuclei themselves and unexplained mechanism of the fusion hindrance, experimentally known since many years ago. On the former, there are rather precise predictions by structure studies, but they are different with each other, so predicted SCE's are not reliable precisely, because 1 MeV difference in them results in change in residue cross section about one order of magnitude through so-called survival probability (It should be noted that fission barrier of SHE is given totally by SCE). On the latter, there was no reaction theory encompassing the hindrance mechanism. The present authors have proposed the two-step model for the fusion process, which explains the hindrance qualitatively [1], and which is applicable to the cold as well as to the hot fusion paths [2]. However, the model overestimates the absolute values of the cross sections, if the masses predicted by P. Moeller et al. [3] are used. Examples of the calculated excitations are shown in Fig. 1 [4] and 2, with only one free parameter f, a factor for SCE, in order to reproduce order of magnitude of the cross sections. As for the formation step of the spherical compound nucleus, the present authors recently have made a closer analysis of fusion dynamics from di-nucleus to mono-nucleus, which improves predictions of fusion probability quantitatively [5]. That is expected to make a free parameter f to be unnecessary to introduce. Furthermore, the neck dynamics is found to depend on mass-asymmetry and thus, fusion probability depends on incident channel with the neck dynamics unknown so far. In connection with the question on which path is more favorable when we proceed to heavier systems, the compound nucleus with Z=120 is an interesting object to study theoretically, because there are three incident systems with different mass-asymmetry. Experiments are under way or are expected to be made in a near future. Theoretical predictions obtained with the refinements by the neck dynamics will be reported for heavier elements not yet measured.(author)

[en] In the present paper, the nuclear softness parameter σ from VMINS mode is calculated

[en] With the motivation of studying complete and incomplete fusion reactions in a ¹²C+⁵⁹Co projectile target system, the excitation functions for (C, p3n), (C, 2p2n), (C, αn), (C, α2n), (C, αp3n) and (C, 2α2n) reactions have been measured up to 80 MeV. The well-known activation technique followed by offline high purity Ge γ-ray spectroscopy was used. The measured experimental values were compared with the statistical model calculations by using the ALICE-91 and CASCADE codes. For the calculations obtained by CASCADE, the variation of parameter F_θ, which is the ratio of actual moment of inertia to the rigid body value have also been studied. Considerable enhancement of the measured excitation functions compared to theoretical predictions for some channels clearly indicates the presence of incomplete fusion with complete fusion in the present projectile energy range. The measurements of forward recoil range distribution of evaporation residues at 80 MeV projectile energy confirm these observations. (author)

[en] Structure at low excitations in near closed shells nuclei is dominated by the excitation of a few valence particles into spherical shell model orbits. Diversely, in beyond shell closure nuclei, quadrupole collective excitations viz. vibrations near the shell closure and rotations in mid shell nuclei, dominate the nuclear structure. However, this picture of low-lying excitations in atomic nuclei is complicated by the presence of coexisting shapes as well as by the intruder configurations. Yrast band energy ratio R_4/2 ≡ E(4₁⁺)/E(2₁⁺) is a most basic signature of the nuclear shapes and has been reported widely as a base of nuclear models. As the valence nucleon number increases this ratio has also been found to increase from R_4/2 < 2 (semi/near magic) to R_4/2 ∼ 3.33 (deformed rotor) passing through the R_4/2 ∼ 2 (spherical vibrator) and transitional nuclei with R_4/2 ∼ 3

[en] Asymptotical methods are used to derive the criterion of Bose-Einstein condensation (BEC) possibility and the criteria determining the order of phase transition at BEC and indicating that BEC can be a phase transition (PTν) of an arbitrary order υ = (2, ∞) with finite or infinite jumps of the κ ν - 1) derivatives of chemical potential μ(T) and total energy E(T) with regard to T and that all this is being determined by parameter χ D/s + g₁^-1⁺...+ q_D^-1 (q_i - are the exponents of calibrating functions of asymptotical behavior of U(r) at the minimum point). Parameter χ takes on an infinite sequence of values (χ_k = k/(k - 1)), setting the Δχ interval in which the BEC is possible, and for each PTνΔχ_ν subintervals of Δχ and on each Δχ_ν there are subintervals where the jumps of μ(T) and E(T) are either finite or infinite. The universal role of parameter χ in systematization of infinite variety of tided systems 'external field-system of bosons' by classes of identical nature of phase transitions at BEC is also shown

[en] For measuring fusion excitation functions, the activation technique with a stack of targets offers the considerable advantage that several reaction energies may be simultaneously measured by using one beam energy. However, its main drawback is the degradation of the beam quality as it passes through the stack due to statistical nature of energy loss processes and any non-uniformity of the stacked targets. If not taken properly into account, this degradation can lead to a wrong determination of the fusion excitation function. In this contribution some results of the investigation of this problem are reported. The present authors suggest as a possible solution to infer the true excitation function, to apply a deconvolution procedure. In order properly apply this procedure a detailed knowledge of the target thickness distribution and of the incoming beam distribution beam must be available