Shapes of the neutron-rich 88-94Kr nuclei

Neutron-rich, ^88-94Kr nuclei, populated in spontaneous fission of ²⁴⁸Cm, have been studied with EUROGAM 2, by measuring prompt γ-rays. Many new excited states in even-even Kr isotopes have been identified. For the first time spins and parities were determined experimentally in these nuclei. Our results indicate that the quadrupole deformation of Kr isotopes will appear only above N = 58, as observed in Sr and Zr nuclei. The newly found 3^- level at 1506.4 keV in ⁹⁰Kr suggests the exsistence of a new region of increased octupole correlations, probably associated with the ν(d _5/2 h _11/2) pair of Δl = Δj = 3 orbitals. Received: 18 September 2000 / Accepted: 18 October 2000     

High-K band structures in 164Er

High-spin states of the doubly-odd ¹¹²Sb were studied by in-beam spectroscopy using the ⁸⁸Sr (²⁸Si, p3n) and ⁸⁹Y (²⁹Si, α2n) fusion-evaporation reactions at beam energies of 120 and 108 MeV, respectively. γ?γ, charged particle-γ?γ coincidences, and γ?γ angular correlation analyses were employed for determining the level scheme of ¹¹²Sb. In the present work, all the levels except for low-lying states in ¹¹²Sb were newly established. Two ΔI = 1 strongly coupled bands were observed; one is a negative-parity band that is similar to those observed in the neighboring doubly-odd Sb isotopes and the other is a positive-parity band that has a new type structure not observed in the other isotopes. From the similarity of the properties of these ΔI = 1 bands to the bands built on 9/2⁺ 2p?1h states in the odd-A Sb isotopes, we suggest that these two ΔI = 1 bands should be associated with the [π(g_9/2)^?1 ? νh_11/2] and [π(g_9/2)^?1νg_7/2] configurations, respectively.     

Hyperfine interactions in the alkaline-earth Sr ions by collinear fast beam laser spectroscopy

The magnetic dipole hyperfine structure constants of the⁸⁷SrII 5s²S_1/2 ground state and the 5p²P_1/2 excited state, and the isotope shifts of the ionic 5s²S_1/2 → 5p²P_1/2 resonance transition for all stable Sr isotopes, measured by collinear fast beam laser spectroscopy, are reported.     

Microscopic study of low-lying yrast spectra and deformation systematics in neutron-rich <Superscript>98–106</Superscript>Sr isotopes

Variation-after-projection (VAP) calculations in conjunction with Hartree-Bogoliubov (HB) ansatz have been carried out for A = 98–106 strontium isotopes. In this framework, the yrast spectra with J ^Π ≥ 10⁺, B(E2) transition probabilities, quadrupole deformation parameter and occupation numbers for various shell model orbits have been obtained. The results of the calculation for yrast spectra give an indication that it is important to include the hexadecapole-hexadecapole component of the two-body interaction for obtaining various nuclear structure quantities in Sr isotopes. Besides this, it is also found that the simultaneous polarization of p _3/2 and f _5/2 proton subshells is a significant factor in making a sizeable contribution to the deformation in neutron-rich Sr isotopes.     

Saturation of deformation atN=60 in the Sr isotopes

From the halflife oft _1/2=3.91 (16) ns for the 2₁ ⁺ state in¹⁰⁰Sr a deformation parameter ofβ=0.40(1) has been derived. Within the given uncertainties, this value is equal to the recently determinedβ-parameters for⁹⁸Sr and⁹⁹Sr, indicating that in the Sr isotopes saturation of deformation is reached immediately at its onset well before neutron midshell. This behaviour is reflected by the “twin” character of⁹⁸Sr and¹⁰⁰Sr with identical features of their unperturbed ground-state rotational bands. These observations are discussed in terms of strong two-nucleon interactions.     

Nuclear spins of76Rb and119Cs byβ radiation detected optical pumping

An optical pumping apparatus has been attached to the reconstructed ISOLDE on-line mass separator at CERN in order to obtain nuclear data of isotopes far fromβ stability. As first results the spins of⁷⁶Rb (T _1/2=36.8 s) and¹¹⁹Cs (T _1/2=37.7 s) have been determined byβ radiation detected optical pumping (β-RADOP) to beI=1 andI=9/2 respectively.     

Hyperfine structure and isotope shift investigations in202–222Rn for the study of nuclear structure beyond Z=82

The hyperfine structure (hfs) and isotope shift (IS) in the isotopic chain of the radioactive element radon have been studied for the first time. The measurements were carried out by collinear fast-beam laser spectroscopy at the mass separator facility ISOLDE at CERN. The IS between 16 isotopes in the mass range 202A222 and the hfs of 7 odd-A isotopes were determined in the transitions 7s [3/2]₂-7p [5/2]₃ (745 nm) of Rn I. The nuclear spins and moments, as well as the observed inversion of the odd-even staggering for^218–222Rn, can be associated with the effects of octupole instability around N=134.This work was supported by the Bundesministerium für Forschung und Technologie and the Deutsche Forschungsgemeinschaft.     

Nuclear spins,moments and charge radii of108−111Sn

The hyperfine structure splittings (hfs) and isotope shifts (IS) in the atomic transitions 5s ² 5p ^{2 1} S ₀ → 5s ² 5p6s ^1,3 P ₁ have been measured for the radioactive isotopes^108?111Sn and all stable ones. The tin isotopes were prepared as fast atomic beams for collinear laser spectroscopy at the GSI online mass separator following a fusion reaction. Nuclear spins, magnetic dipole, electric quadrupole moments and changes in mean square charge radii have been determined. In¹⁰⁹Sn the spinI=5/2 was measured for the nuclear ground state (T _1/2=18 min) in contradiction to the literature value. The mean square charge radii show a parabolic behaviour with a maximum at N=66. This is interpreted by collective effects, which are considerably stronger than accounted for by theB(E2)-values.     

Estimate of the wavelengths for the first and second resonance lines in the francium I spectra

Relativistic self-consistent-field wavefunctions have been used to calculate one-electron eigenvalues for the ground s-state, the first and the second excited p-states of Sr II, Cs I, Ba II, Fr I and Ra II. When knowing the difference between the experimental energies and the theoretical ones for Sr II, Cs I, Ba II and Ra II the wavelengths for the first and second resonance lines in Fr I have been estimated with the following result: λ(7²P_1/2? 7²S_1/2)=812±10) nm λ(7²P_3/2? 7²S_1/2)=719±10) nm λ(8²P_1/2? 7²S_1/2)=433±5) nm λ(8²P_3/2? 7²S_1/2)=423±5) nm     

Structure of the highly deformed nucleus101Sr63 and evidence for identical K=3/2 bands

The low-energy level scheme of theN=63 nucleus¹⁰¹Sr has been obtained from a β-decay study of¹⁰¹Rb. The ν[532]5/2 and ν[411]3/2 orbitals are well established as the ground state and a band head at 271.2keV, respectively. The general properties of the level scheme indicate a quadrupole deformation ofβ ? 0.4, confirming the unique feature of saturation of deformation inN ≥ 60 Sr isotopes. The energies of theK=3/2 intraband transitions in the odd-neutron neighbours⁹⁹Sr₆₁ and¹⁰¹Sr₆₃ are very similar. More generally, the identical bands at low spin in^98–101Sr nuclei are correlated with the mass-independent moments of inertia in this region.     

The decay of127Cs

The decay of¹²⁷Cs (T _1/2=6.2 h) was investigated by means of a Ge(Li) spectrometer and a double-focusingβ-ray spectrometer. The decay scheme for¹²⁷Cs is presented including eight new levels. The spins and parities for¹²⁷Xe levels were determined. Based on the determination of the spins for the ground and first excited levels the spin 9/2 for the isomeric state of¹²⁷Xe was proposed. The relative cumulative yields of caesium isotopes from the spallation of natural cerium with 660 MeV protons are given.     

On theβ − decay of the 2s isomer in98Y and the existence of an intruder band in98Zr

The γ radiation from the ß^? decay of the high-spin isomer in⁹⁸Y has been studied at the separator JOSEF. A main goal was to get insight into the spins of levels in⁹⁸Zr which have been interpreted as members of an intruder band based on the 0₂ ⁺ state at 854 keV. The measuredγ-γ angular-correlations lead to the assignment of spins of 4 and 3 ? to the 2491 and 1844 keV levels, respectively, and contradict their interpretation as the 6⁺ and 4⁺ states of the proposed band. For the 2.0s isomer of⁹⁸Y, the ß{?}-decay properties suggest I=5 with a major configuration [πg_9/2,νs_1/2(g² _7/2)₀].     

Nuclear spins and magnetic moments of some neutron-deficient rubidium isotopes

The nuclear spins and magnetic moments of some neutron-deficient rubidium isotopes have been measured by atomic-beam magnetic resonance techniques at the ISOLDE facility, CERN. The following results have been obtained: ⁷⁷Rb, $\text{I =}\text{3}\text{2}\text{, μ}{}_{\mathrm{I}}\text{= 0.652(7)}\text{n.m.}$; ⁷⁸Rb, I = 0; ^78mRb,I = 4, μ_I = 2.56(3)(rmn.m.); $\text{(su79)}\text{Rb}\text{, I =}\text{5}\text{2}\text{, ifμ}{}_{\mathrm{I}}\text{= 3.364(4)}\text{n.m.}\text{,}\text{and}{}^{\mathrm{<mtext>84</mtext><mtext>m</mtext>}}\text{Rb}\text{, I = 6}$.The data on the The data on the light rubidium isotopes gives evidence for deformed nuclear shapes     

Nuclear moments of strongly deformed strontium isotopes

Nuclear spins, moments and mean square charge radii of^78–100Sr have been obtained by fast ion-beam collinear laserspectroscopy. The experiments performed at ISOLDE have been extended to include⁹⁹Sr, measured by a non-optical detection scheme with a two-step optical pumping sequence. The results for the strongly deformed isotopes are discussed in the frame of the particle-plus-deformed core model.     

Alpha-decay characteristics of neutron-deficient 190Po, 189Bi and 186Pb isotopes

The neutron-deficient ¹⁹⁰Po and ¹⁸⁹Bi isotopes have been produced in the 2n respectively p2n channels of the ⁴⁸Ti +¹⁴⁴ Sm reaction. Cross sections for different reaction channels are given. For ¹⁹⁰Po, improved values of α-energy E_α = 7550(15) keV and half-life T_1/2 = 1.9 _?0.4 ^+0.6 ms were measured. By using correlated α-decay chains an α-branching ratio of 0.50(25) was deduced for ¹⁸⁶Pb. The reduced α-width systematic is extended for both of these isotopes, confirming a persistence of the saturation towards the lighter Po isotopes and the absence of any anomalies for the neutron-deficient Pb isotopes. For ¹⁸⁹Bi improved values of E_α = 7300(15) keV and T_1/2 = 4.8(5) ms were measured.     

Deformation in the light Br isotopes

The nuclear ground state spins of the odd-A Br nuclides^{75, 77, 79}Br with Z=35 are all 3/2⁻. Nilsson orbital calculations show that the 35^th proton occupies the f_5/2 [301]3/2⁻ orbital for ε<0.20 and the p_3/2 [312]3/2⁻ orbital at larger deformations. The magnetic moments of these two states differ by a factor of two, giving clear evidence for the magnitude of the ground state deformation. Low Temperature Nuclear Orientation measurements made in Oxford and Bonn on^{76, 77g}BrFe prepared at ISOLDE, and on line at the SERC Daresbury Laboratory on^{72, 74m, 75}BrFe, have yielded the magnetic moments of these isotopes, using a two non-zero field model with magnetic hyperfine fields of +81.38(6) T and 26(2) T. The spin of the⁷³Br ground state is also deduced. An interpretation of the ground state configurations of these isotopes is given.     

Possibility of separating the isotopes127I and129I with the aid of a photodissociation iodine laser

A method for separating iodine isotopes is proposed, based on the large difference between the rate constants of the excited I*(²P_1/2) and unaxclted iodine atoms with radicals CF₃ and with Cl₂ molecules, and on the possibility of selectively acting on the₁₂₇I atoms in the states²P_1/2 and²P_3/2 by radiation from a photodissociation R¹²⁷I iodine laser (λ = 1.315 μm). The possibility of separating the pure isotope¹²⁹I and the mixture¹²⁷I with¹²⁹I is investigated.     

Structure of 4,4′-butane-(1,4,7-three-p-tolylsulphonyl-1,4,7-three amine) diphthalonitrile

Abstract

The crystal structure of the title compound, C₄₁ H₃₅ N₇ O₆ S₃ was determined as monoclinic by single crystal X-Ray diffraction technique. The molecular structure was identified by IR, ¹H-NMR, ¹³C-NMR and elemental analysis. The crystal parameters of this compound are as follows: monoclinic P 2 1/n, a = 12.694(2) Å, b = 26.204(2) Å, c = 13.005(2) Å, β = 102.95(2)°, V = 4216.02(1) Å.³, Z = 4, Dx = 1.289 g/cm³, F(000) = 1704, λ (MoKα) = 0.71070 Å, μ = 0.2 mm^?1. The structure was solved by SHELXS-97 and refined by SHELXL-97. R = 0.06 for 3178 observed reflections with I > 2σ (I).     

Laser spectroscopy and mass measurements on alkali isotopes

Isotope shifts, spins, hyperfine structures and masses have been measured for the series of the alkali isotopes including the nuclei far from stability. The method of laser spectroscopy and its combinations with rf excitation are described. Some results are discussed, namely the first observation of the red doublet D₁-D₂ of francium, and the study of shell effects and changes of shape with mass and δ〈r ²〉 measurements for Rb and Na isotopes.     

Yrast band spectroscopy of155Gd and157Dy

The yrast bands of¹⁵⁵Gd and¹⁵⁷Dy have been observed to high spins (I～25–40). The systematic properties of the N=91 isotones with particular reference to the second i_13/2 neutron and first h_11/2 proton alignments are discussed.