Observation of a fission-like process in the bombardment of48Ti and50Ti by32S

Heavy reaction products (A≧38) were studied in the bombardment of^48,50Ti by³²S at 105, 130 and 144 MeV beam energies. At 130 and 144 MeV, fragments are observed which have angular and kinetic energy distributions consistent with those expected from fission of the composite system (A ～ 80).     

Predominant time scales in fission processes in reactions of S, Ti and Ni with W: zeptosecond versus attosecond

The inhibition of fusion by quasifission is crucial in limiting the formation of superheavy elements in collisions of heavy nuclei. Time scales of ～10(-18) s inferred for fissionlike events from recent crystal blocking measurements were interpreted to show either that quasifission itself is slower than previously believed, or that the fraction of slow fusion-fission is higher than expected. New measurements of mass-angle distributions for (48)Ti and (64)Ni bombarding W targets show that in these reactions quasifission is the dominant process, typically occurring before the system formed after contact has made a single rotation, corresponding to time scales of ≤10(-20) s.     

Observation of the double-charge-exchange reaction48Ca(32S,32Si)48Ti atE lab=125 MeV

The impact parameter (b) dependence of K-shell vacancy production probability for 1,5 MeV/u Nb on Mo collisions has been measured. Consistent with previous experiments on other high Z collision systems, the shape of the b-dependence shows significant deviations from the two-state 2p?-2pσ rotational coupling model.     

Discrete γ-rays in the reactions of 143 MeV32S with58Ni

The reactions induced by 143 MeV³²S on⁵⁸Ni have been studied detecting discrete γ-rays in coincidence with projectile-like fragments (PLF). Information on PLF excitation probability and sequential decay of target-like fragments (TLF) has been obtained. For the²⁸Si+⁶²Zn outgoing channel at small energy loss (¦Q¦<20 MeV), both PLF and TLF data indicate that thermal equilibrium is not attained. The hypothesis of an equal excitation energy partition between the two reaction fragments does not describe properly experimental TLF data. A dependence of PLF excitation probability on the outgoing channel is found for the two final channels³²S+⁵⁸Ni and²⁸Si+⁶²Zn. The values of the spin alignment parameterP _zz, derived for PLF and TLF from measurements ofγ-rays anisotropy, are in disagreement with the expectations of the transport theory for dissipative collisions.     

Projectile-like fragments excitation and gamma-rays emission after the deep inelastic reaction of32S on58Ni

The deep-inelastic reaction induced by 143 MeV³²S on⁵⁸Ni have been studied detecting projectile-like fragments (PLF) in coincidence withγ-rays in NaI(TI) scintillators. γ-ray multiplicity and anisotropy have been derived for Z_plf=14, 15 as a function of energy loss and/or γ-energy. The information obtained are compared with a discrete γ-line study of the same reaction. The effect of the exit channel selection (ejectileZ, energy loss,E _γ) on the γ-observables is discussed in connection with the evidence of a strong PLF γ-emission.     

Damped oscillations in the energy autocorrelation functions of the 58Ni+46Ti elastic and 58Ni+62Ni elastic and inelastic scattering cross sections

Structures of non-statistical character, recently observed in ⁵⁸ Ni +⁴⁶ Ti elastic and ⁵⁸ Ni +⁶² Ni elastic and inelastic excitation functions, produce damped oscillations in the cross section energy autocorrelation functions. The analysis of these damped oscillations in terms of S-matrix spin and parity decoherence indicates, as a possible interpretation, damping of the coherent rotational motion of the intermediate dinuclear system formed in the reaction.     

The critical phenomenon and the re-entrance phenomenon in the anti-tumor model induced by the time delay

The effects of time delay τ on an anti-tumor model driven by a multiplicative noise and a periodic signal are investigated. The results obtained from the small delay approximation and numerical simulations indicate: (i) For the absence of the periodic signal in the system, the two-peak structure of the stationary probability distribution transforms into the single-peak structure with the increasing τ, and τ exists a critical value τc. For τ<τc, the stationary mean value 〈x〉_st of the cell population decreases as the noise intensity D increases, however, for τ>τc, the 〈x〉_st increases as the D increases; (ii) For the presence of the periodic signal in the system, the structure of the signal-to-noise ratio with changes of the D exhibits the transitions of one peak → two peaks → one peak as τ increases.     

Investigation of the electronic characteristics of Ni3 (Fe,Ti) and Ni3 (Mn,Ti) alloys

The anomalous Hall (R_s) and the Nerst-Ettingshausen (Q_S) constants are measured for hardened Ni₃ (Fe, T_i) and Ni₃ (Mn, Ti) alloys. Scattering by phonons is detected, con tributing primarily to R_S as compared to scattering by magnetic inhomogeneities. Based on the positive signs of R_g and Q_S, it is concluded that 3d holes wi th antiparallel spin make the main contribution to the conductivity. A model is proposed for the electronic structure of the alloys studied.DeceasedTranslated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 59—63, June, 1981.     

The Kα and Kβ X-ray spectra of Al,Ti, Cr,Fe and Ni induced by 84 MeV nitrogen ions

The K X-rays from the target elements due to N-ion bombardment are measured with a crystal spectrometer. Some aspects owing to high incident energy are discussed. The Kα satellite, Kα hypersatellite and Kβ satellite peak spacings are obtained.     

A study of the (t,p) reactions leading to 48Ti and 50Ti

Angular distributions of the proton groups from the ⁴⁶Ti(t, p) and ⁴⁸Ti(t, p) reactions have been measured at incident triton energies of 9.64 and 11.14 MeV, respectively, using a multi-angle magnetic spectrograph. Nine distributions of the stronger groups from the ⁴⁶Ti(t, p) reaction were measured leading to states of ⁴⁸Ti up to an excitation of5.50 MeV. For the ⁴⁸Ti(t, p) reaction distributions of 24 stronger groups were measured up to an excitation of 8.29 MeV in ⁵⁰Ti.The results have been analysed using plane wave, two-nucleon stripping theory and many L-value assignments have been made. The results are compared with the corresponding (d, p) reactions in all cases where comparisons may be made the l_n values from the latter agree with the (t, p) L-values.For both (t, p) reactions the ground state groups are strong and are formed by L = 0, two-neutron transfer. The low lying excited states are very weak in both reactions but strong L = 0 transitions were observed to the 4.97 MeV excited state of ⁴⁸Ti and to the 3.88 MeV state of ⁵⁰Ti. Neither of these states is appreciably excited in the corresponding (d, p) reaction. A discussion on the possible structure of these states and the occurence of similar states in neighbouring nuclei has been reported previously¹).     

First observation of the neutron-rich nuclei42Si,45, 46P,48S,and51Cl from the interaction of 44 MeV/u48Ca +64Ni

Five new very neutron-rich isotopes,⁴²Si,^45,46P,⁴⁸S and⁵¹Cl, are identified from the interaction of a 44 MeV/u⁴⁸Ca beam with a⁶⁴Ni target.     

X射线荧光光谱法测定不锈钢中的组分

用X射线荧光光谱法测定了不锈钢中Si、Mn、P、Cu、Ti、W、Mo、V、Ni、Cr、Nb等11种元素的含量。对磨样条件、准确度和精密度进行了实验,实验表明本方法与化学法所测结果相符。     

An investigation of excited states in32S by the31P(p, γ)32S reaction

The³¹P(p, γ)³²S reaction has been studied in the proton energy region 300–1420 keV using Ge(Li)-techniques. Gamma decay schemes of 16 resonances are proposed. The branching ratios of the resonance states and 23 bound states are presented. The spin of theE _x=7116 keV level was found to beJ ^π=2⁺. In addition, the present results are compared with earlier ones.     

Polarization in the elastic scattering of 12 MeV deuterons by 12C, 56Fe and 58Ni

Angular distributions are presented of the vector polarization of 12 MeV deuterons elastically scattered by ¹²C, ⁵⁶Fe and ⁵⁸Ni for lab scattering angles 20–160°. The vector polarized deuteron beam from the Birmingham Radial Ridge Cyclotron polarized deuteron source was used, and the experimental method involved frequent “on-off” switching of the polarization at the source. Asymmetries were measured, using semiconductor detector telescopes in the scattering plane, against simultaneous readings of a carbon polarimeter whose analysing power was calibrated by means of the d-⁴He scattering. Large values of polarization were observed for ¹²C; the medium-weight nuclei ⁵⁶Fe and ⁵⁸Ni showed characteristic oscillatory patterns of lower amplitude. An attempt was made to explain the results in terms of optical-model predictions, and the calculations seem to favour a potential for deuterons approximating the sum of the proton and neutron optical model potentials.     

Investigation on surface compositions of CuNi alloy under Ar+ ion bombardment by ISS and in situ AES measurements

Surface compositions of CuNi(50 wt%) alloy under 3 keV Ar⁺ ion bombardment were measured by Auger electron spectroscopy (AES) and ion scattering spectroscopy (ISS). In situ AES measurement of sputter-deposited layer and sputtered sample surface indicated that surface composition became Ni-rich due to Ar⁺ ion sputtering at steady state, in accord with previous reports of preferential sputtering. ISS measurements with 3 keV Ar⁺ ions, however, have suggested that the composition of the outermost atom layer is not Ni-rich but slightly copperrich. This leads to the conclusion that the degree of preferential sputtering is small and that the question of preferential sputtering, particularly, the ratio of the sputtering yields, $\text{S}{}_{\mathrm{<mtext>Cu</mtext>}}\text{S}{}_{\mathrm{<mtext>Ni</mtext>}}$, based on AES measurement requires further examination.     

Emission of X-ray continua by bombardment of thick Al,Si and Ti targets with protons and14N ions

Using thick targets the continuous X-ray spectra arising in the collision systems Al+p (0.5–7 MeV), Si+p (0.6–6 MeV), Si+¹⁴N (6 MeV, 14 MeV), Ti+p(1 MeV) and Ti+¹⁴N (14 MeV) were measured by means of a Si(Li) detector. Total yields were derived and compared with numerical results of calculations for secondary electron and nuclear bremsstrahlung. For Si and Ti the continuous spectra from one and the same target bombarded with protons and¹⁴N ions of equal velocity were investigated. Drastic deviations from theZ ₁ ² scaling have been found. They could be attributed to contributions of MO radiation originating by recoil of target atoms. The influence of characteristic line profiles on the measured spectra is also discussed.     

Optical absorption measurements of the transition metals Ti,V, Cr,Mn, Fe,Co, Ni in the region of 3p electron transitions

Using the continuous spectrum of synchrotron radiation, the absolute absorption coefficient of seven transition metals has been determined in the spectral range 40–300eV. The strong oscillations reported by previous investigators appear to have been spurious.