Level structure of 76Br from the 75As(α,3nγ) reaction

Hitherto unknown states of ⁷⁶Br were excited through the (α, 3nγ) reaction on ⁷⁵As at E_α = 30 to 55 MeV. Excitation functions, γ-ray angular distributions, γ-γ coincidences and the γ-ray emission time with respect to the beam bursts were determined. Levels above the 1^? ground state at energies (in keV) with the following spin-parity assignments are proposed: 141.8, 2; 253.7, 3^?; 491.8, 4; 584.9, 5^?; 1016.3, 6. These levels exhibit the energy spacings of a Coriolis-perturbed rotational band and the branching ratios show collective behavior. The comparison of these levels with those of the $\text{5}\text{2}$⁺ ground-state band recently reported in ⁷⁷Kr show that (a) the Coriolis effects are quite similar and (b) the first two excited levels lie very close in energy in both cases. The possibility that these two facts indicate the validity of the rotation aligned coupling scheme in a doubly odd system is discussed.     

Level structure and lifetimes of low-excitation states in 63Cu

The lifetimes of 9 states in ⁶³Cu up to an excitation energy of 2092 keV have been determined by means of the Doppler-shift attenuation method using the ${}^{60}\text{Ni}\text{(α,}\text{p}\text{γ)}$ reaction. A search was made for a suitable set of M1 and E2 single-particle matrix elements for use with shell-model eigenstates throughout the Ni, Cu and Zn isotopes. The theoretical predictions for the level spectroscopy and electromagnetic transitions and static moments in ⁶³Cu are in satisfactory agreement with the experimental findings.     

Energy levels in As from the As(p,d) As reaction

The ⁷⁵As(p, d) ⁷⁴As reaction has been used to identify 23 excited states in ⁷⁴As. The l_n values, or mixture of l_n values, to 19 levels have been determined from DWBA fits. The spectroscopic sum rules show a neutron shell filling which is consistent with other N = 42 isotones.     

A study of low-lying states of 76As using the 75As(d,p) reaction

The ⁷⁵As(d, p)⁷⁶As reaction was investigated with 11 MeV deuterons. Thirty levels of the residual nucleus were identified up to about 1.8 MeV excitation energy, and angular distributions were measured. Spectroscopic factors and l_n values were obtained for low-lying transitions by means of a distorted-wave analysis of the differential cross sections. The l_n = 4 transition to the ground state of ⁷⁶As and the presence of l_n = 2 transitions to low-lying levels provide a strong support to the assumption that nuclei in this mass region have a large deformation parameter. The results are compared with the ⁷⁵As(n, γ)⁷⁶As data.     

The level structure of the 153Gd nucleus studied in the 150Sm(α, n)153Gd reaction

The level structure of ¹⁵³Gd has been studied by means of the ¹⁵⁰Sm(α, n)¹⁵³Gd reaction. The experiment included measurements of γ-γ coincidences, γ-angular distributions, γ-ray yield at 17 MeV and 19 MeV beam energy, and γ-ray multiplicities. Favoured and unfavoured members of the positive-parity i_13,2, band were identified. States belonging to the h_9,2 and f_7,2 band structures have been located.Surprisingly low multiplicity numbers were deduced for ₁₅₃Gd γ-rays. This may indicate that the (α, n) reaction is not a pure compound reaction. The level structure of ¹⁵³Gd has been compared to the known structure of other odd-mass N = 89 nuclei, and a close similarity is found.The positive-parity band structure has been compared to calculations with the pairing-plus-recoil model. Good agreement is obtained without any ad hoc Coriolis attenuation.     

Level structure of 100Tc

Gamma and electron spectra following thermal neutron capture on ⁹⁹Tc have been studied with a bent-crystal spectrometer, Ge(Li) and Si(Li) detectors and a magnetic spectrometer. Prompt and delayed γ-γ coincidences with Ge(Li) detectors have been performed. A level scheme is proposed for ¹⁰⁰Tc comprising 21 excited states up to 640 keV. The binding energy of the last neutron in ¹⁰⁰Tc was deduced. For most levels, spin and parity values were assigned. Two isometric transitions of respective half-lives 10.2 and 4.6 μs have been identified using the ¹⁰⁰Mo(d, 2n)¹⁰⁰Tc reaction with a pulsed beam of deuterons. From the comparison of the present (n, γ) study and the collaborative study of the ⁹⁹Tc(d, p) reaction, several members of the multiplets $\text{π}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{ν}\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$, $\text{π}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{ν}\text{g}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$, $\text{π}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{ν}\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and $\text{π}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{ν}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ have been identified.     

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.     

The 75Se(n, γ)76Se reaction and the low-lying level structure of 76Se

The ⁷⁵Se(n, γ)⁷⁶Se reaction was studied through consecutive neutron capture with the use of pair and curved crystal spectrometers. The high-resolution data have allowed construction of a very well established level scheme including many new levels above ～ 2.8 MeV excitation energy. The resulting neutron binding energy, 11154.0 ± 0.3 keV, is lower than the value given in the mass table. The ⁷⁵Se(n, γ) cross section was determined to be 330 ± 100 b. The level scheme and branching ratios were compared with results from calculations in the framework of the interacting boson model.     

Level structure of 99Tc by inelastic scattering and proton stripping

The ⁹⁸Mo(³He, d)⁹⁹Tc and ⁹⁹Tc(d, d') reactions have been used to study the levels of of ⁹⁹Tc. Spin-parity assignments are made for nearly all states below 1.5 MeV excitation. Strong j-dependence is noted for l = 1 transitions in the proton stripping reaction, making possible several new spin assignments. The inelastic scattering data on ⁹⁹Tc are compared to similar data on ⁹⁸Mo, and are found to be in agreement with a coupling scheme based on a shell model with good seniority.     

A dynamic analysis of spontaneous-fission half-lives

Spontaneous-fission half-lives of even-even heavy nuclei (Z = 92–110) are calculated without any adjustable parameters. The fission-barrier penetration is treated as a one-dimensional problem in multidimensional deformation space. Deformations of multipolarities 2, 3, 4, 5 and 6 (describing elongated, necked and reflection asymmetric shapes of a nucle'us) are considered. The potential energy is calculated by the macroscopic-microscopic method and the inertia tensor by the cranking method. The action integral is minimized by variational procedures.The barrier heights are reproduced with an accuracy better than 1.5 MeV and the half-lives to within a factor of about 50, on the average.     

On the possibility of detecting superheavy quasimolecules

The formation of superheavy electronic quasimolecules leads to measurable deviations from the Rutherford cross section in heavy ion collisions. For the system ²³⁸₉₂U-²³⁵₉₂U with E_c.m. = 800 MeV we find an average correction of 1.5% for the scattering cross section in forward directions. Additional background contributions like electronic shielding of the nucleus, vacuum polarization, nuclear Coulomb excitation and static deformations of the nuclei are taken into account.     

The magnetic moment of the first excited state of 19O

The magnetic moment of the first excited 96 keV, $\text{3}\text{2}{}^{\mathrm{+}}$ state of ¹⁹O has been determined by an integral perturbed angular correlation measurement in a transverse external magnetic field. The value obtained for the g-factor, ?0.48(6), is discussed in terms of shell-model configurations. The wave function of the $\text{3}\text{2}{}^{\mathrm{+}}$ level is shown to consist mainly of the $\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^3$ configuration.     

Gamma-decay modes of Ne

The lifetimes of the 3376 and 3576 keV states in ¹⁸Ne have been investigated by the Doppler-shift recoil-distance method using the ¹⁶O(³He, n)¹⁸Ne reaction. The 3376 keV level has τ_m = 4.4 ± 0.6 ps and the 3576 keV level has τ_m < 6 ps. In addition the ground state branch of the 3616 keV level has been observed to be (12.5 ± 2.5) %. Furthermore it was found that δ(3616 → 1887) = +0.03 ± 0.09. These results are compared with theoretical predictions.     

Problems of angular momentum projection in nuclear physics

In nuclear models approximate wave functions are often used which do no have sharp angular momentum as required of the exact wave functions. It seem obvious that model wave functions of this type should be improved by projection onto states of good angular momentum. It is not the purpose of this paper to discuss the technical difficulties of projection (which can be formidable for many particle systems), but rather to present in an elementary way certain fundamental ambiguities in the use of projection. An application to high spin states near the yrast line is suggested.     

Multiple coulomb excitation of 167Er

The ground-state rotational band in ¹⁶⁷Er has been investigated through multiple Coulomb excitation with a 160 MeV ³⁵Cl beam. Excited states up to $\text{25}\text{2}{}^{\mathrm{+}}$ were established by measuring γγ coincidences and γ-ray angular distributions. Gamma-gamma angular correlations were also measured. Nuclear lifetimes of levels up to spin $\text{23}\text{2}$ have been determined from Doppler-broadened γ-ray lineshapes, and B(M1) and B(E2) values of intra-band transitions deduced. Considerable signature dependence was observed for level energies and M1 transition probabilities. A Coriolis band-mixing calculation was carried our for comparison with the experimental results. The measured M1 transition probabilities are compared to calculations based on a particle-rotor model, a cranking model, and a microscopic model with quantum-number projection.     

Isospin-forbidden particle decays in light nuclei: (II). Widths of T = 32 levels of 17O

The lowest four $\text{T =}\text{3}\text{2}$ levels of ¹⁷O have been observed as resonances in the ¹³C(α, n)¹⁶O reaction. Excitation energies and widths obtained for these levels are 11.076 ± 0.005 MeV, Γ_c.m. = 5.0 ± 1.1 keV; 12.458 ± 0.005 MeV, Γ_c.m. = 8 ± 2 keV; 12.944 ± 0.006 MeV, Γ_c.m. = 6 ± 2 keV; 12.993 ± 0.006 MeV, Γ_c.m. < 3 keV. The total and partial decay widths for the lowest $\text{T =}\text{3}\text{2}$ level are much larger than those of the analogue level in ¹⁷F, implying significant isotensor components in the $\text{T =}\text{1}\text{2}$ admixtures.     

Radiochemical investigation of the mass distribution and probability in stopped μ− induced fission of 238U

Radiochemical measurements of 24 fission products show that the mass-split is asymmetric in stopped μ^? induced fission of ²³⁸U. The mass distribution is similar to 14 MeV neutron-induced fission. The main difference is a smaller peak-to-valley ratio no point indicating a mean excitation energy of about 20 MeV. The fission probability (prompt and delayed) is 0.15 ± 0.03 per stopped muon.