Measurement of g-factors in 170Yb, 172Yb and 174Yb by transient field interaction at high recoil velocities

A beam of ⁴⁰Ca ions at 168 MeV has been used to Coulomb excite high-spin states in ¹⁶⁹Tm and ^{170, 172, 174}Yb which recoiled through thin polarized iron at ν/c ≈ 3.5%. An enhanced transient field ≈ 6 times larger than the Lindhard-Winther prediction was observed and calibrated against the known g-factors in ¹⁶⁹Tm. Individual g-factors could not be extracted because of strong feeding; nevertheless, deviations from rotational behaviour (constant g-factors) would be detectable. Empirical fits to microscopic calculations of the rotational g-factors below spin 12⁺ suggest that if deviations from the simple rotational formula occur, they should be of the form g(J) = g₀(1 + αJ²). We find the following values in ^{170, 172, 174}Yb: α × 10³ = ?0.5±1.5, +1.0±1.5. The uncertainties are the level at which deviations from rotational behaviour are expected to occur. The results are discussed in terms of Coriolis anti-pairing effects.     

Electrodisintegration of 3He

Double differential cross sections for electron-³He scattering leading to continuum states were measured between break-up threshold and the region of quasi-free interaction in a momentum transfer range of $\text{1}\text{fm}{}^{\mathrm{?2}}\text{< ¦}\text{q}\text{¦}{}^2\text{< 2.5}\text{fm}{}^{\mathrm{?2}}$. The cross sections for the quasi-free scattering calculated in plane-wave impulse approximation were found to be in good agreement with the experimental results for momentum transfer $\text{¦}\text{q}\text{¦ > 1.5}\text{fm}{}^{\mathrm{?1}}$.     

Measurement of the 50Cr(γ, n)49Cr cross section with monochromatic γ-rays

The ⁵⁰Cr(γ, n)⁴⁹Cr cross section has been measured over the energy range E_γ = 20.43 to E_γ = 22.22 MeV using monochromatic γ-rays from the ³H(p, γ)⁴He reaction and detecting the resulting ⁴⁹Cr positon activity. The γ-rays were monitored by a 12.7 cm × 15.2 cm NaI(Tl) crystal. The positon activity was determined by a coincidence detector consisting of two 7.62 cm × 7.62 cm NaI(Tl) crystals set on the annihilation radiation photopeaks. The γ-ray energy resolution was less than 110 keV over the whole energy range. Structure in the cross section was not observed.     

A 7.3 ms isomer of 161Lu

An isomer of ¹⁶¹Lu with a half-life of 7.3 ± 0.4 ms has been discovered in the heavy-ion reaction ¹⁴⁸Sm(¹⁹F, 6n)^161mLu. Oneγ-ray transition with energy 135.8 ± 0.2 keV was observed, and a K-conversion coefficient of 1.1 ± 0.3 deduced in the decay of this isomer.     

The analysing power of the reaction pp → πd for proton energies between 500 AND 600 MeV

The analysing power A_y0 of the pp → πd reaction has been measured at SIN for four energies between 516 and 582 MeV with a statistical precision of better than 1%. Pions and deuterons have been detected in coincidence with scintillation detectors employing time-of-flight techniques for event identification. Using our data on the differential cross section σ, Legendre polynomial expansion coefficients b_j^y0 for the product σA_y0 have been deduced for j = 1 to 5. The energy dependence of these coefficients has been compared with theoretical predictions.     

Ground and γ-vibrational bands in even Os isotopes (A = 182–188) studied by (α, χnγ) and (p, χnγ) reactions

Gamma rays following ¹⁸²W(α, 2n)¹⁸⁴Os, ¹⁸⁴W(α, 2n)¹⁸⁶Os, ¹⁸⁶W(α, 2n)¹⁸⁸Os, ¹⁸⁵Re (p, 2n)¹⁸⁴Os, ¹⁸⁵Re(p, 4n)¹⁸²Os, ¹⁸⁷Re(p, 2n)¹⁸⁶Os and ¹⁸⁷Re(p, 4n)¹⁸⁴Os reactions have been measured to study the ground and γ-vibrational bands in even Os isotopes (A = 182–188). In addition to the ground-state levels the γ-vibrational bands have been identified up to the 5⁺ members. The K = 4 band head is proposed in ¹⁸⁶Os and ¹⁸⁸Os.     

Photoreactions of 16O in self-consistent RPA theory: (III). Polarized (γ, p) and (γ, n) angular distributions and inverse capture reactions below 60 MeV

Polarized ¹⁶O(γ, p₀) and ¹⁶O(γ, n₀) reactions below 60 MeV are analyzed in the framework of a self-consistent RPA theory with the Skyrme force Sk3. The calculations include dipole and quadrupole transitions in LWA. Asymmetries, polarizations and analyzing powers are calculated and compared with the available experimental data. Our aim is to show to what extent polarized results give additional information to that extracted from the unpolarized ones, both on the many-body structure of the nucleus and on the nature of the reaction mechanism at intermediate energies.     

Band structures in 98Ru and 99Ru

The level schemes of ^{98, 99}Ru were studied with the reactions ⁹⁸Mo(α, 3nγ) and ⁹⁸Mo(α, 4nγ) at E_α = 35 to 55 MeV, using a large variety of in-beam γ-ray detection techniques and conversion-electron measurements. A search for the 3^? state was carried out with the reaction ⁹⁸Ru(p, p′). The ground-state band of ⁹⁸Ru was excited up to J^π = (12)⁺ and a negative-parity band up to (15)^?. New levels in ⁹⁸Ru were found at E_x = 2285 (J^π = 4⁺), 2435 (J^π = (3^?, 4⁺)), 2671, 3540, 4224, 4847, 4915 (J^π = (12)⁺), 4989 (J^π = (12⁺)), 5521 (J^π = (13)^?), 5889, 6591 (J^π = (15)^?), and 7621 keV. New unambiguous spin and parity assignments were made for the levels at E_x = 2014 and 3852 keV, as J^π = 3⁺ and 9^?, respectively. New levels in ⁹⁹Ru were found at E_x = 1976, 2021 ($\text{J}{}^{\mathrm{\pi }}\text{= (}\text{15}\text{2}{}^{\mathrm{+}}\text{)}$), 2393, 2401 ($\text{J}{}^{\mathrm{\pi }}\text{= (}\text{17}\text{2}{}^{\mathrm{+}}\text{)}$), 2875 (π = (+)), 3037, 3201 ($\text{J}{}^{\mathrm{\pi }}\text{= (}\text{23}\text{2}\text{)}{}^{\mathrm{?}}$), 3460 ($\text{J = (}\text{17}\text{2}\text{)}$), 3484 ($\text{J}{}^{\mathrm{\pi }}\text{= (}\text{21}\text{2}{}^{\mathrm{+}}\text{)}$), 3985, 4224 ($\text{J}{}^{\mathrm{\pi }}\text{= (}\text{27}\text{2}{}^{\mathrm{?}}\text{)}$), and 5359 keV. The 1070 keV, $\text{J}{}^{\mathrm{\pi }}\text{=}\text{11}\text{2}{}^{\mathrm{?}}$ level in ⁹⁹Ru has a half-life of 2.8 ns. A strongly excited negative-parity band is built on this level. A positive-parity band based on the ground state was excited up to $\text{J}{}^{\mathrm{\pi }}\text{= (}\text{21}\text{2}{}^{\mathrm{+}}\text{)}$. The level schemes are well reproduced by the interacting boson model in the vibrational limit.     

Phase-shift analysis of 16O + 16O elastic scattering

A phase-shift analysis has been carried out for ¹⁶O + ¹⁶O elastic scattering, resulting in unambiguous values for the reflection coefficients in the energy range of the first gross structure of the 90° excitation function, and answering some of the questions still open regarding the calculations existing so far.     

7Li + 54Fe Single-nucleon stripping reactions at E = 48 MeV

Angular distributions have been measured for the ⁵⁴Fe(⁷Li, ⁶Li/⁶He)⁵⁵Fe, ⁵⁵Co reactions at $\text{E(}{}^7\text{Li) = 48}\text{MeV}$. Exact finite-range DWBA calculations for both reactions, employing Woods-Saxon real and imaginary potentials to generate the distorted waves, reproduce the shape of the f-state angular distributions but not the rate of fall-off with increasing angle for p-states. Using real potentials constructed by double-folding a microscopic nucleon-nucleon potential with a Woods-Saxon shaped imaginary potential to generate the distorted waves did not change the calculations. The forward angle (⁷Li, ⁶He) data allowed the $\text{2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ states in ⁵⁵Co to be located and the determination of the single-particle centroid energies. The ⁵⁵Co spectroscopic factors are in good agreement with those from the (d, n) reaction but are generally 25 % lower than those from average (³He, d) results. The ⁵⁵Fe spectroscopic factors are in good agreement with (d, p) results.     

Energy levels of 94Ru observed with the 96Ru(p,t) reaction

The level structure of the neutron-magic nucleus ⁹⁴Ru, up to an excitation energy of 4 MeV, has been studied by means of the (p, t) reaction. Particular emphasis was placed on a search for excited 0⁺ levels, none of which have been reported previously. Among new levels observed in this study are 0⁺ levels at 2.995, 3.615 and 3.770 MeV, and the 3^? octupole vibration at 2.965 MeV.     

High-spin states in the isotones 89Zr, 91Mo and 93Ru populated in α-particle-induced reactions

The reactions (α, 3nγ) and (α, α′nγ) on ⁸⁸Sr, ⁹⁰Zr and ⁹²Mo were used to populate excited states in ⁸⁹Zr, ⁹¹Mo and ⁹³Ru. The de-excitation of these states was studied by in-beam γ-ray spectroscopy. The short-lived radioactivity of the ⁹²Mo target was measured in order to study the decay of ⁹³Ru. Many new levels were observed, particularly in ⁹¹Mo. They are interpreted as due to the coupling of a $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ neutron hole with known excited states in ⁹⁰Zr, ⁹²Mo and ⁹⁴Ru.     

Semiclassical analysis of the spin polarization of 12B in the 100Mo(14N, 12B)102Ru reaction

Polarization of ¹²B in the ¹⁰⁰Mo(¹⁴N, ¹²B)¹⁰²Ru reaction at 90 MeV incident energy is studied on the basis of the semiclassical theory of transfer reactions proposed by Brink. Gross behaviors of both the polarization and the cross section as functions of product kinetic energy can be predicted successfully by the theory. But disagreement in the numerical values of the polarization is found for low-energy ¹²B.     

High spin collective excitations in 101Ru

The energy level structure of ¹⁰¹Ru was studied using the reactions ¹⁰⁰Mo(α, 3n)¹⁰¹Ru and ¹⁰⁰Mo(³He, 2n)¹⁰¹Ru. Excitation functions, γγ coincidences and γ-ray angular distributions were measured. Three ΔI = 2 cascades proceeding to a $\text{5}\text{2}{}^{\mathrm{+}}$, $\text{7}\text{2}{}^{\mathrm{+}}$ and $\text{11}\text{2}{}^{\mathrm{?}}$ state were observed. A decay scheme is presented showing energies up to 5849 keV and spins up to $\text{35}\text{2}$. The bands are discussed within the framework of the Nilsson model with Coriolis coupling in which the recoil effect has been properly introduced.     

Compound transfer and direct transfer reactions induced by 17O on 13C

The elastic scattering, inelastic scattering, single-neutron transfer reactions ¹³C(¹⁷O, ¹⁶O) ¹⁴C, ¹³C(¹⁷O, ¹⁸O)¹²C and ¹³C(¹⁷O, ¹⁸O_{2+, 1.98})¹²C, and seven other exit channels which involve ⁷Li, ⁹Be, ¹¹B and ¹⁵N have been measured for the system ¹⁷O+¹³C at 12.9 and 14 MeV c.m. It is shown that all reactions mentioned above have significant contributions from compound nuclear decay, following fusion of projectile and target.     

Study of proton transfer reactions to low-lying multiplets in 90Y and 92Nb

The (d, ³He) and (α, t) proton transfer reactions on ⁹¹Zr were studied at incident energies of 24.3 and 35.4 MeV, respectively. Angular distributions were measured from 6° to 50° (⁹⁰Y) and 60° (⁹²Nb). High detection efficiency and good energy resolution were obtained by using a magnetic spectrograph in connection with a multiwire proportional chamber. For the low-lying multiplet levels in both nuclei angular momentum transfers and spectroscopic factors were determined by DWBA analysis. In ⁹²Nb the states at 0, 0.135, 0.29, 0.36 and the sum of the states at 0.48 and 0.50 MeV show typical l = 4 shapes. They belong to the ($\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{π}$)($\text{2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{ν}$) sextet. The corresponding multiplet in ⁹⁰Y is weakly populated ($\text{dσ}\text{dΩ}\text{≦ 20 μb/sr}$), and l = 4 shapes are found for the levels at 0.68, 0.78, 0.95, 1.05 and 1.30 MeV proving previous assignments. The members of the low-lying ($\text{2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{π}$)($\text{2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{ν}$) doublets in ⁹⁰Y and ⁹²Nb exhibit a characteristic l = 1 angular shape. The levels at 1.42, 1.57, 1.64, 1.76 and 1.81 MeV in ⁹⁰Y are excited both by l = 1 and l = 3 resulting from a strong mixing of the ($\text{2}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{π}$)^?1($\text{2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{ν}$) and $\text{(1}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{π)}{}^{\mathrm{?1}}$ ($\text{2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{ν}$) multiplets. Only the level at 2.03 MeV displays a pure l = 3 shape. From the spectroscopic information on the ($\text{2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{π}$)($\text{2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{ν}$) and ($\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{π}$)($\text{2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{ν}$) multiplets in ⁹⁰Y and ⁹²Nb the g.s. configuration mixing in ⁹¹Zr is deduced.     

Heavy ion induced transfer reactions on 148Nd

Transfer reactions induced by ¹⁶O and ¹⁸O beams on ¹⁴⁸Nd were measured with a time-of-flight setup at 72 MeV incident energy. The angular distributions are bell shapes having their maxima at angles somewhat below the grazing angle. The excitation in the final nuclei takes place (if possible) near the optimum Q-value and is spread over 5 MeV for the one-particle transfer reactions and up to 10 MeV for the multiparticle transfers. The cross sections for the individual channels are explained mostly by Q-window considerations. In spite of the differences in the individual channels the total transfer cross section integrated over excitation energy, angle, and all channels turns out to be the same same for both ¹⁶O and ¹⁸O beams. This cross section amounts to 20 % of the total reaction cross section and nicely fills the gap between the measured fusion cross section and the total reaction cross section obtained from optical model calculations based on elastic scattering data.     

Microscopic study of heavy-particle transfer reactions: The (16O, α) reactions on 16O and 28Si

The transfer reactions ²⁸Si(¹⁶O, α)⁴⁰Ca and ¹⁶O(¹⁶O, α)²⁸Si have been studied within the framework of the two-channel generator coordinate method. The geometry of the reactions has been discussed in terms of the cross-channel overlap kernels of the generating functions. A clear connection between maxima in the reaction rate and entrance channel resonances has been established. A two-step reaction mechanism involving quasimolecular resonances of inelastic ¹⁶O-¹⁶O channels is discussed as a possible explanation for narrow structures seen in the ¹⁶O(¹⁶O, α)²⁸Si reaction cross section.     

Energy dependence of multinucleon transfer reactions induced by 20Ne on 12C

The energy dependence of up to five nucleon transfer reactions induced by ²⁰Ne on ¹²C has been measured in the energy range 150 to 294 MeV. Good agreement is found between the experiment and both DWBA and semiclassical calculations.