Nuclear spectroscopic studies of the 23.7 h 248Bk

Main features of the decay of the 23.7 h ²⁴⁸Bk have been determined by spectroscopy with scintillation and semiconductor detectors. The results are as follows: half-life 23.7 ± 0.2 h; branching is (30 ± 5)% to ²⁴⁸Cm (≈ 23% EC decay to 0⁺ ground state and ≈ 7% to first 2⁺ state) and (70 ± 5)%β^? decay to ²⁴⁸Cf(5 % to 592 keV K^π = 2^? state and (65 ± 5)% to the ground-state band). The β^? decay energy, Q_β^?, has been measured to be 860 ± 20 keV, and the electron capture decay energy, Q_EC, has been derived from closed cycle to be 705 ± 25 keV. The deduced logft values of β^? and EC transitions restrict the spin of the ²⁴⁸Bk ground state to 1, with configuration assignment $\text{{}\text{n}\text{[734]}\text{9}\text{2}{}^{\mathrm{?}}$; $\text{p}\text{[633]}\text{7}\text{2}{}^{\mathrm{+}}$. It has also been deduced that the long lived isomer lies 65 ± 40 keV abovethe 23.7h ²⁴⁸Bk ground state.     

Energy levels of the nucleus 250Bk from residual interaction studies

The bandhead energies of twenty two-quasiparticle states expected to occur in the low-energy excitation spectrum of the doubly odd nucleus ²⁵⁰Bk are calculated using a zero-range residual interaction and the results are compared with the available experimental information. Configuration assignments to nine intrinsic states reported in earlier studies are confirmed. Our calculations support the excitation energy of 115 keV for the K^π = 3⁺ state and also the characterisation of the 317 keV 5⁺ state as the K^π = 5⁺ bandhead. In addition, we suggest acceptable two-particle configurations for the 175 keV 1⁺ state and the 216 keV 0⁺ state. The expected location of eight as yet unobserved two-quasiparticle states is predicted.     

Identification of the new isotope 241Bk

A new neutron-deficient berkelium isotope ²⁴¹Bk produced in the ²³⁹Pu(⁶Li, 4n) reaction has been identified using a gas-jet coupled on-line isotope separator. Cm K and L X-rays associated with the EC decay of ²⁴¹Bk were observed in the mass-241 fraction, and three γ transitions were attributed to the EC decay of ²⁴¹Bk through X-γ coincidences. The half-life of ²⁴¹Bk was determined to be 4.6±0.4 min which is 1/2-1/4 of that of theoretical predictions. The half-life value and the observed γ transitions can be consistently explained as a consequence of the allowed EC transition of π7/2⁺[633] → ν7/2⁺[624]. Received: 14 October 2002 / Accepted: 6 November 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: asai@tandem.tokai.jaeri.go.jp Communicated by J. ?yst?     

Structure of levels of the 160Gd nucleus

The scheme of excited levels of the ¹⁶⁰Gd nucleus was refined and extended owing to the addition of the K _?? = 2^? band and the inclusion of new rotational states in other bands. Data for the respective (n, n???) reaction from the literature were used. The signature splitting of K = 1 bands was found.     

Energy levels of francium

Many-body perturbation theory is used for relativistic calculations of energy levels and of fine-structure intervals for 20 lower states of francium. The zeroth-order approximation is obtained by the relativistic Hartree-Fock method. The second-order correlation corrections are calculated. The accuracy for the s, p and f energy levels is not worse than 0.5%.     

Energy levels of Si

Proton energies and strengths of (p, γ), (p, p₁), (p, p₂) and (p, ₁γ) resonances of the ²⁷Al + p reaction were determined for E_p < 2.5 MeV. The γ-decay of 78 resonances and 46 bound levels was established and four new bound levels were found at E_x = 9793.8±2.0, 10513.5±1.0, 10884.1±2.0 and 11778.8±1.5 keV. The level at E_x = 11.43 MeV was found to be a doublet. Lifetimes of 25 bound levels were measured by means of the Doppler-shift attenuation technique. Angular distributions were measured at 15 resonances.     

Energy levels of Tm

Fifty-one levels in Tm¹⁶⁸ have been observed up to an excitation energy of 1514 keV utilizing 12-MeV deuterons and the reaction Tm¹⁶⁹(d, t)Tm¹⁶⁸. The Q value of the lowest observed state was determined to be −1776 ± 15 keV. The spectrum below 700 keV has been interpreted in terms of the coupling of the [411↓] Nilsson proton orbital with the neutron orbitals prominent in the low-energy (d, t) spectrum of Er¹⁶⁷. This interpretation has resulted in the determination of relative energies due to the residual neutron-proton interaction for six different configurations. The observed singlet-triplet splitting energies for the [633↑], [521↓], and [512↑] neutron orbitals coupled to the [411↓] proton orbital were measured to be −157, +191, and −234 keV, respectively. Theoretical calculations of these energies made for a zero range spin-dependent central potential gave values of −87, +154, and −255 keV, respectively. The good agreement indicates that the spin-spin interaction can account for most of the singlet-triplet splitting energy.     

High-spin levels in the odd-odd nucleus142Eu

High-spin states up to I=22? have been observed for the first time in the odd-odd nucleus¹⁴²Eu above the 8^? β⁺ -decaying isomer. A new isomer of mean life τ_m=9.0± 0.6 ns and J^π=8⁺ has been identified. The low energy part of the level scheme is interpreted in terms of single-particle excitations in the 2d_5/2 and h_11/2 orbitals and of the N=80 core excitations.     

Characterization of energy levels in the nucleus170Lu

Configuration assignments are derived for the observed energy levels in the odd-odd deformed nucleus¹⁷⁰Lu₉₉ based on the calculations of the two-particle band head energies for a zero range residual interaction, the beta-feeding characteristics, and the observed features for similar bands in the neighbouring nuclei. In particular, specific assignments are given for theJ ^π =1⁺ levels at 198.4 keV, 349.0 keV and 785.5 keV. The ambiguities with respect to the assignments for theK ^π=3⁻ bands are discussed. A new isomer withJ ^π =7⁺ and half-life of several seconds is predicted around (225±25) keV and experiments are suggested to identify it.     

Energy splitting of the ground-state doublet in the nucleus 229Th

The energy splitting of the 229Th ground-state doublet is measured to be 7.6+/-0.5 eV, significantly greater than earlier measurements. Gamma rays produced following the alpha decay of 233U (105 muCi) were counted in the NASA/electron beam ion trap x-ray microcalorimeter spectrometer with an experimental energy resolution of 26 eV (FWHM). A difference technique was applied to the gamma-ray decay of the 71.82 keV level that populates both members of the doublet. A positive correction amounting to 0.6 eV was made for the unobserved interband decay of the 29.19 keV state (29.19-->0 keV).     

Energy levels of 37K

Angular distributions have been measured for six ³⁶Ar(p,γ)³⁷K resonances in the E_p = 0.9−3.0 MeV energy region. These experiments yield spin- and parity assignments to seven excited states of ³⁷K, γ-ray branching ratios for each state, together with the multipolarity mixing ratios of most transitions. Lifetimes have been deduced from the same data with the DSA method.Excitation energies have been determined with a precision up to 20 eV. A resonance- and excitation-energy measurement at the E_p = 918keV resonance yields a ³⁶Ar(p, γ)³⁷K Q-value of Q = 1857.57 ± 0.09 keV.The ³⁶Ar(p, p₁γ) yield curve, measured in the E_p = 2.6–3.3 MeV region, yields additional information on resonance and excitation energies of ³⁷K states with a typical precision of 0.6 keV.The new data on ³⁷K levels allow a detailed comparison of the level schemes of the mirror nuclei ³⁷Ar and ³⁷K. The present experimental data agree quite well with the results of previous shell-model calculations.     

Energy levels of bound polarons

A new variational wave function to describe the ground state and the excited states of a bound polaron is proposed. It is of the form

$\text{|Ψ〉 = c|O〉|ø}{}_{\mathrm{n}}\text{〉 +}\text{∑}\text{g}{}_{\mathrm{k}}{}^1\text{V}{}_{\mathrm{k}}{}^1\text{(e}{}^{\mathrm{<mtext>i</mtext><mtext>k·r</mtext>}}\text{? ρ}{}_{\mathrm{k}}{}^1\text{)a}{}_{\mathrm{k}}{}^{\mathrm{+}}\text{|O〉|ø}{}_{\mathrm{n}}$

. It is argued that this form is reasonable for all electron—phonon coupling α and all strengths β of the Coulomb potential. Numerical and analytical results are derived for the energy of the ground state and compared to existing results. Results for the energy of the lowest p-type excited state of the bound polaron are obtained.     

Energy levels of175Hf

The reaction¹⁷⁵Hf(d, t)¹⁷⁵Hf was studied using 12 MeV deuterons from the Florida State University super FN tandem Van de Graaff accelerator. The outgoing tritons were analyzed by means of a Browne-Buechner type broad range magnetic spectrograph. Twenty-four states in¹⁷⁵Hf have been identified and fifteen states have been given wave function assignments on the basis of the spectroscopy associated with rotational band structure in deformed odd-A nuclei. TheQ-value for the reaction was measured to be ?1925±8 keV.     

Low-lying intrinsic energy levels in the nucleus170Ho

The band-head energies of the two-quasiparticle states expected in the doubly odd deformed nucleus¹⁷⁰Ho are calculated for a zero range residual interaction. The results are compared with the available experimental information. It is concluded that the ground state has the Nilsson configuration 6⁺{7/2^?[523↑] _p }+5/2[512↑] _n being the 2.76m isomer whereas the 43s isomer is the 1⁺ ∑=0 state arising from the same configuration and lies at about 100 keV excitation energy in agreement with the experiment. The first excited state in this nucleus is predicted to be the 4^?{3/2⁺[411↑] _p +5/2^?[521↑] _n } state close to the ground state with the corresponding 1^? ∑=0 member expected to appear well above the 1⁺ isomer.     

In-beam study of low-lying levels in the149Sm nucleus

The¹⁴⁶Nd(α,n) reaction combined with conventional in-beam spectroscopic methods has been used to study low-lying levels in¹⁴⁹Sm. Several new levels andγ-ray transitions have been placed to the¹⁴⁹Sm level scheme. Main features of levels below 1 MeV in¹⁴⁹Sm have been reproduced in a quasiparticle-rotor model calculation.     

Excited levels in the neutron deficient nucleus111Sb

The level scheme of the neutron deficient isotope¹¹¹Sb up to about 3.7 MeV is established from in-beam gamma-ray spectroscopy experiments. The identification of the reaction channel using cross bombardments:⁹⁵Mo+¹⁹F (56–68 MeV),¹⁰⁶Cd+⁷Li (20–30 MeV),¹⁰²Pd+¹¹B (45 MeV), charged partice-γ and neutron-γ coincidences is discussed.     

The lifetime of strongly overlapping compound nucleus levels

We show how to express the lifetime of a compound nucleus in terms of the transmission coefficients. We have derived this result in the absence of doorway states and direct reactions. Our formalism shows that the decay width is then equivalent to the correlation width.     

Medium-spin levels in the N=83 nucleus147Gd

Zeitschrift für Physik A Hadrons and nuclei - Levels of theN=83 nucleus147Gd have been investigated by methods of in-beamγ-ray and conversion electron spectroscopy using the147Sm(3He, 3n)...     

Energy levels in46Ti

The gamma-ray spectra of several resonances in the⁴⁵Sc(p, γ)⁴⁶Ti reaction were measured using a 5 cm³ Ge(Li) detector. A thick target was bombarded with 1377 and 1660 keV protons, several resonances were therefore excited at each proton bombarding energy. The decay and energy of 30 excited levels were investigated. The intensity of all transitions to the ground state agrees within an error of about 9% with the total intensity of all transitions starting from the proton capture states, which indicates that low energy transitions between high-excited levels are of no importance. We have calculated a theoretical primary gamma-ray spectrum that fits the experimental averaged spectrum rather well.