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.     

Crystal blocking measurements of the time delay of fission induced by 32S, 48Ti, and 58Ni bombardment of W

The time delay in fission induced by bombardment of W with 180 MeV 32S, 240-255 MeV 48Ti, and 315-375 MeV 58Ni has been measured by observation of crystal blocking. There is a clear narrowing and a small increase in the minimum yield of the angular dips for fission compared with scaled dips for elastically scattered ions. This is interpreted as a fission delay of about 2 as, only weakly dependent on energy and atomic number. The delay is longer by 1 to 2 orders of magnitude than obtained from standard interpretations of measurements of prescission neutrons and giant-dipole-resonance gamma rays and from calculations of the nuclear dynamics in heavy-ion reactions.     

Intermediate mechanisms in fission-like fragmentation in the 32S + 59Co and 32S + 63Cu reactions

The fission-like fragmentation of the ³²S + ⁵⁹Co and ³²S + ⁶³Cu composite systems has been studied at incident energies E/A ≈ (4–5) MeV/nucleon. Mass, energy and angular distributions of the fission-like fragments were obtained from time-of-flight measurements. The mean total kinetic energies of the fragments are found to be fully relaxed, whereas a strong angular dependence is observed in the mass distributions. The data are interpreted in terms of a dynamical model based on the transport theory.     

Inner-shell ionization ofZ=25–32 elements by 5-48 MeV32S ions

TheK-shell ionization cross sections of Mn, Ni, Cu, Zn and Ge under³²S bombardment have been measured in the energy range from 5 to 48 MeV. The cross sections are compared with available theories based on a direct Coulomb ionization mechanism and with the predictions of theK-vacancy sharing process. This last process can reasonably account for the measured cross sections at high bombarding energies. The energy shifts of theK _α- andK _β-lines and theK _α/K _β-intensity ratios have also been measured. This information is used to deduce the defect configuration of the atoms. The mechanisms responsible for the multiple vacancy production are discussed.     

Fission characteristics of the composite system 32S+50Ti: (I). Correlations between coincident fragments

The characteristics of “fission-like” processes observed in the bombardment of ⁵⁰Ti with ³²S ions of 140 MeV energy are investigated in a coincidence experiment between a time-of-flight telescope and a position sensitive ΔE-E ionization chamber. Coincident particles were identified and their energy and angular correlations in and normal to the reaction plane were measured. The experiment proves the binary nature of the mass division. Both the width and the average value of the total kinetic energy distribution are consistent with the values extrapolated from fission of heavier nuclei. An average number of 3±1 nucleons are emitted during the reaction; α-particle emission is not an important decay mode.     

Structural modification of TiAlN coatings by preliminary Ti Ion bombardment of a steel substrate

The TiAlN coatings deposited onto steel 12Cr18Ni9Ti substrates before and after preliminary treatment by Ti ion beams are studied by X-ray diffraction, transmission electron microscopy, atomic force microscopy, and nanoindentation. The modification of the surface layer of a substrate is shown to change the structure and the preferred orientation of the coatings. The mechanical properties of the TiAlN coatings are found to depend substantially on the ion bombardment time.     

Secondary ion emission from organic films under bombardment with a 32S beam at 3 MeV/A

Abstract

An experimental investigation of the secondary ion emission from organic films under heavy ion bombardment at high energies was carried out by using a time-of-flight mass spectrometer coupled to a Tandem heavy ion accelerator. Preliminary results obtained at 3 MeV/A are reported and discussed.     

Electroexcitation of magnetic dipole and other modes in46Ti and48Ti

With high-resolution inelastic electron scattering measurements on⁴⁶Ti and⁴⁸Ti the excitation mechanism of the transition into low lying J^π=1⁺ states is investigated. The experimental evidence of considerable contribution of the orbital part of theM1 operator to the total transition strength is given by a model dependent analysis of form factors. The possibility of physical relationship to low lying J^π=1⁺ states in the rare earth nuclei is discussed in various models. MoreoverE2 form factors and good candidates forM3 form factors are presented.     

A study of photoreactions in 48Ti

A high resolution measurement of the ⁴⁸Ti(γ, n) cross section is reported. Evidence for isospin splitting of the giant dipole resonance is found to be consistent with the prediction. In addition the deformation splitting of the GDR is consistent with predictions of the dynamic collective model.     

Damage zone produced by the bombardment of stainless steel using Ti nitride PVD coatings

This paper presents the damage zone and defects produced by TiN thin film deposition on stainless steel using DC magnetron sputtering to produce collisions between the TiN ions and the substrate. The PVD process used a low operative pressure, reducing the bombardment damage on the substrate, in comparison with other methods.Internal friction (IF) and elastic modulus measurements were carried out in TiN-PVD coated AISI 304 stainless steel, using a sub-resonant torsion pendulum (f ≅ 1 Hz) and a vibrant-reed instrument (f ≅ 10³ Hz). Some experiments showed several internal friction peaks, which are attributed to dislocation relaxation and to martensitic transformation from γ to α′. The characterization was carried out with X-ray, AFM and SEM. Analysis of X-ray peaks indicates a residual deformation in the order of 0.0005-0.0009 for γ-phase and 0.0006-0.00204 for α′-phase. Two methods are presented to determine the adhesion energy by IF in coated materials: for the first the enthalpy is determined by means of isochronal IF measurements, while for the second it is determined using isothermal measurements. These produce an image of damage caused by the bombardment on the substrate, especially of the residual defects.     

The influence of non-radiative transitions on bombardment induced photon emission from Ti and Ti oxide

Photon yields from Ti atoms sputtered from Ti and Ti oxide due to 55 keV Ar⁺ and O₂⁺ ion bombardment have been studied. Photon yields and line profiles of selected lines have also been studied as a function of background O₂ exposure. An attempt has been made to correlate changes in yields and line shapes with variations of the band structure in the solid. Resonance ionization processes are shown not to contribute to the observed yield, however Auger processes cannot be excluded. Lifetime effects have a strong influence on the observed results. It is shown that the distribution of excited states produced by the ion bombardment is Boltzmannlike. We note that it is possible to interpret these results in terms of a model which assumes that the probability of excitation or ionization is exponentially dependent on the excitation or ionization energy, without invoking electron exchange mechanisms.     

Observation of the proton-pairing vibration in 48Ca

The two-proton transfer reaction (¹⁴C, ¹⁶O) has been investigated at 96 MeV on targets of ⁵⁰Ti and ⁴⁸Ca. The ⁴⁸Ca states at 0 MeV (0⁺), 3.83 MeV (2⁺), 4.28 MeV (0⁺) and 4.50 MeV (3⁻) and the ⁴⁶Ar ground state were excited. The 4.28 MeV 0⁺state has a transfer strength comparable to the g.s. transition to ⁴⁶Ar and a predominant proton vibrational character. The interpretation of the state as the proton-pairing vibrational state is supported by estimates of the excitation energy based on experimental binding energies.     

Level structure and lifetimes of excited states in 48Ti

The properties of excited states in ₂₂⁴⁸Ti₂₆ populated by means of the ⁴⁵Sc(α, pγ)⁴⁸Ti reaction were investigated. The Doppler-shift attenuation method was employed to determine the mean lives of 16 levels up to an excitation energy of 4073 keV. Proton-γ coincidence techniques were used to record simultaneously the Doppler-shifted de-excitation γ-rays emitted at 26 and 154 degrees to the incident beam direction. A comprehensive level and decay scheme is proposed. Detailed shell-model calculations have been made of M1 and E2 transition matrix elements for depopulation of states whose lifetimes have been measured. Salient nuclear structure aspects of this “self-cross-conjugate” nucleus are examined in light of critical comparisons of measured and calculated Ml and E2 reduced transition probabilities.     

Exact calculation of the mass distribution in the collision process of32S on medium-weight nuclei

This work deals with the exact integration of a Fokker-Planck equation for the mass distribution in heavy ion collisions. The results are compared to those obtained in a previous calculation in which the distribution is approximated by its two lowest moments.     

Structural evolution of Ti50Cu50 on rapid cooling by molecular dynamics simulation

The structural evolution and atomic structure of the Ti₅₀Cu₅₀ compound have been investigated by means of molecular dynamics simulation using the generalized embedded-atom model (GEAM) potential. Gibbs free energy calculation manifests the large driving force of undercooled Ti₅₀Cu₅₀ for crystallization and thus the poor glass-forming ability. Radial distribution functions (RDFs) within the temperature range from 2000 K to 300 K are analyzed and reveal the increasing degree of short-range order and reducing periodic length between peaks on cooling. Atomic arrangement is characterized by the Voronoi tessellation method, showing that the frequency of icosahedral configurations is most sensitive to temperature and grows upon quenching while that of the others remains relatively stable. The thermal behavior of the structure factors follows the Debye model up to the supercooled liquid temperature. The structural investigation of amorphous Ti₅₀Cu₅₀ demonstrates that there exist a variety of polyhedral configurations in Ti₅₀Cu₅₀ amorphous alloy, where icosahedral and bcc clusters are the major types. Due to the existence of bcc clusters and the other distorted polyhedra other than full icosahedra, the structural analysis reconfirms the inference from the Gibbs free energy calculation.     

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.     

Experimental equation of state of the shape memory alloy Ti50Ni48Fe2 AT 0-8 GPa and 298 K

The influence of hydrostatic pressures (up to 8 GPa) at 298 K on the pressure curves of the volume and volume elastic modulus of the B2 phase of Ti₅₀Ni₄₈Fe₂ single crystals is investigated by an ultrasonic pulse-phase technique. It is proposed on analysis of the results that the alloy undergoes a B2→R martensitic, transition at 4.0–5.4 GPa. It is shown that the universal equation of state accurately describes the pressure dependence of volume over the entire pressure range. Institute of Strength Physics and Materials Science, Siberian Division, Russian Academy of Sciences. Institute of High-Pressure Physics, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 48–53, August, 1997.     

Prediction of a shape isomeric band in32 S

We predict a rotational shape is omeric band in³²S, and propose as 0⁺, 2⁺, 4⁺ candidates the already known levels at 8.507, 9.065 and 10.276 MeV.