Z. Vager

Precession measurements following Coulomb excitation with oxygen ions (VI). Hyperfine interactions of nuclei in highly ionized atoms

Abstract Measurements are reported of angular distributions of gamma rays from excited 2 + states of various nuclei recoiling into vacuum or gas. The angular distributions are found to be perturbed by strong hyperfine fields generated by the highly ionized atoms. Both in vacuum and in gas, the interaction is found to be predominantly magnetic dipole and of a rapidly fluctuating character. In gas, the fluctuations in the field direction are due to collisions (at the rate of about 2 × 10 13 sec −1 at atmospheric pressure), and in vacuum they are brought about by optical transitions (at a rate of about 3 × 10 11 sec −1 ). The average hyperfine field of Nd or Sm emerging from a solid target with 10 MeV kinetic energy is found to be 25.5 ± 2.5 MG. Measurements of g -factors of 2 + excited states have been carried out, and the values of g -factors (relative to g( 152 Sm )) are reported for 150 Sm, 154 Sm, 148 Nd and 150 Nd.

Energy loss of protons in rare earth oxides and reduced transition probabilities for 2+→0+ transitions in even rotational nuclei

Measurements of gamma yields from thick targets of rare earth oxides bombarded by protons were combined with lifetime measurements to determine reduced E2 transition probabilities in 2/sup +/ - 0/sup +/ rotational transitions. The rate of energy loss of the protons in the target was determined by a measurement of the absorption of the gamma in the target material at different proton energies yielding the mean penetration of the protons into the target. (auth)

Analogue resonances of odd cadmium isotopes

Abstract A study of analogue resonances by elastic proton scattering from 106 Cd, 108 Cd, 10 Cd, 112 Cd, 114 Cd and 116 Cd is reported. Resonance parameters were extracted and spectroscopic factors were derived. The method used for calculating single-particle widths is discussed as are the systematics of the obtained spectroscopic factors.

Study of low-lying states in cadmium isotopes by (p, p' γ) angular correlation via analogue resonances

Abstract Correlation measurements of inelastic protons, from even cadmium isotopes via analogue resonances, and 2+ → 0+ γ-rays are reported. The analysis takes into account compound enhancement and yields partial decay amplitudes. The latter are interpreted as amplitudes in a fractional parentage expansion of the parent analogue states.

E2/M1 mixing ratios and K conversion coefficients of some rotational transitions

Abstract The E2/M1 mixing ratios and K conversion coefficients of the first two rotational transitions in Eu153 and Ho165 have been measured by observing the decay of the second rotational level in these nuclei. This level was Coulomb excited and its decay by two cascade transitions was detected in a coincidence arrangement. The mixing ratios were determined from the angular distributions of the two gamma rays. The same coincidence arrangement was used to measure the K conversion coefficients of these transitions. The E2/M1 mixing ratio of the 110 keV transition in Tm169 was also determined. The following results were obtained: Eu153−δ(109 keV = 0.585±0.050, αK(83.4 keV) = 2.34±0.13, αK(109 keV) = 1.15±0.09; Ho165−δ(95 keV) = 0.173±0.036, δ(114 keV) = 0.171±0.032, αK(95 keV)= 2.64±0.10, αK(114 KeV) = 1.49±0.07; Tm169-δ(110 keV) = −0.146±0.016. In the case of Ho165 and Tm169 the experimental mixing ratios agree with predictions of the rotational model. This is not true for Eu153. The measured K conversion coefficients are in good agreement with theoretically calculated values.

Precession measurements following Coulomb excitation with oxygen ions: (V). Hf ions recoiling into liquid gallium

Abstract Precession measurements were carried out for the 2 + states in 176 Hf, 178 Hf and 180 Hf. The nuclei were excited by oxygen ions of 34 MeV and embedded by recoil into liquid gallium which was found to provide an unperturbed environment.

The incoming wave boundary condition for elastic scattering of heavy particles at incident energies near the coulomb barrier

Abstract An incoming wave boundary condition (IWB) approach is used to calculate differential cross sections for 16O + Ca and α + Pb elastic scattering, at incident energies near the Coulomb barrier. A comparison is made to optical model (OM) calculations and it is shown that the present method is competitive with the OM method in the energy region mentioned above.

Elastic scattering of 16O and 18O by even Ca isotopes, 52Cr and 62Ni at incident energies near the Coulomb barrier

Abstract The excitation functions measured in this experiment show marked differences between 16O and 18O. The experimental data are analysed and discussed by means of an incoming-wave boundary-condition method (IWB).

A time-to-pulse-height converter with simultaneous random coincidence subtraction

Abstract A coincidence circuit capable of simultaneous registration or subtraction of random coincidences is described. The coincidence circuit is based on a time-to-pulse-height converter. The design of a time-to-pulse-height converter for use with NaI(Tl) scintillation counters is given. Random coincidences are counted during the coincidence experiment proper. Systematic errors in determining the number of random coincidences are smaller than 0.5%. The resolving time of the system is 6 ns for the 0.51 MeV line of Na22. The circuit performs satisfactorily at counting rates up to 50 000 per second.

Coulomb explosion of 11.2 MeV OH+ in carbon foils

Abstract Combined energy and angle distributions of protons resulting from Coulomb explosion of 11.2 Mev OH+ in carbon foils have been measured in simultaneous coincidence with different emerging oxygen charge-states. The measurements were made with targets of thickness ranging from 80 A to 740 A. The proton distributions show strong asymmetry effects due to the electronic wake produced by oxygen atoms in the solid, and there is also a marked dependence of the shape of the distributions on both the target thickness and the oxygen charge-state downstream from the target.