High-spin two-quasiparticle bands in76Br

Excited states of the doubly-odd nucleus V6Br have been studied with in-beam γ-ray spectroscopy techniques. In addition to the positive parity band that has been extended up to I=(13) a I^π=4^? isomer (T_1/2=0.5±0.2 ns) and two bands of negative parity have been identified. The bands are discussed in terms of two-quasiparticle configurations. For the band built on the 4_? isomer the configuration πg9/2?νf5/2 or p3/2 is proposed.     

The decay of 74Kr

The decay of ⁷⁴Kr has been studied. Its half-life was determined to be $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 11.50 ± 0.11}\text{min}$. A decay scheme is proposed, based on γ-γ and β⁺-γ coincidence measurements, which takes account of 99 % of the strength of 57 observed γ-rays. The total decay energy was measured to be Q_EC = 3327 ± 125 keV. The decay feeds the (0, 1)^?, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 25.3}\text{min}$ isomer of ⁷⁴Br.     

The N = Z nuclide 74Rb with T,Iπ = 1, 0+

Improved experimental techniques have permitted the observation of the new nuclide ⁷⁴Rb with a half-life of 64.9 ± 0.5 ms, which represents the heaviest self-conjugate nucleus detected until now. The absenceof along-lived isomer indicates that the T = 0 state of ⁷⁴Rb lies a bove the T = 1 state. An upper limit of 10^?3 relative top ⁷⁴Rb can be placed on the yield of the (unobserved) mirror nucleus ⁷³Rb, and it appears likely that the limit of particle stability has been reached. The half-life of ⁷⁵Rb is 17.0 ± 1.0 s.     

Level structure of170Er observed in the decay of the 2.76 min170Ho

TheΒ ^?-decay of the longer-lived¹⁷⁰Ho isomer produced through the¹⁷⁰Er(n, p)¹⁷⁰Ho reaction has been investigated by using a versastile detector and coincidence equipment. The half-life andΒ ^?-decay energy were determined to beT _1/2=2.76±0.05 min andQ _β =3.85±0.15 MeV, respectively. In addition to the ground state band and some higher energy levels, the proposed level scheme of¹⁷⁰Er contains 11 states between 1.0 and 1.6 MeV (6 new ones), which are connected mutually by previously unknown low-energy transitions. Spin and/or parity assignments based mainly on coincidence data and multipolarity determinations are suggested for most of these states. By using systematic considerations and the nuclear projection model calculations several bands withK≧2 can be assigned tentatively. As a side result the half-life of¹⁶⁹Ho was determined to be 4.7 ±0.2 min.     

Mean life of the 854 keV 02+ state in 74Se and the coexistence model

The mean life of the first excited 0₂⁺ state in ⁷⁴Se, only 219 keV above the first excited 2⁺ state at 635 keV, was measured to be 1.2±0.2 nsec, with delayed coincidence techniques. The 0₂⁺ state was populated by the decay of ⁷⁴Br produced via the ⁶⁰Ni(¹⁶O, pn)⁷⁴Br reaction. The extracted B(E2; 0₂⁺ → 20₁⁺) value is 14±2 s.p.u. which suggests that the 0₂⁺ state is collective. Application of a coexistence model in terms of spherical and deformed shapes is discussed for ⁷⁴Se.     

Nuclear excitation by electron transition in 189Os

A precise experiment on nuclear excitation by electron transition (NEET) was first performed on ¹⁸⁹Os. An osmium film was bombarded with electrons of 72–100 keV to measure the absolute values of the cross section for osmium isomer (^189mOs) production. The threshold energy for this process is 74 keV, and the cross section is, e.g., 1.1 nb at 100 keV. The NEET probability derived from the measured excitation function is (1.7 ± 0.2) × 10^?7     

Isomers of astrophysical interest in neutron-deficient nuclei at masses A = 81, 85 and 86

Decay properties of neutron-deficient exotic nuclei close to A=80 have been investigated at the IGISOL facility. The studied nuclei, ⁸¹Y, ⁸¹Sr, ^81mKr, ⁸⁵Nb, ⁸⁵Zr, ⁸⁶Mo and ⁸⁶Nb, were produced by a ³²S beam from the Jyv?skyl? isochronous cyclotron on ⁵⁴Fe and ^natNi targets. The internal conversion coefficient for a 190.5 keV isomeric transition in ^81mKr has been measured and the internal transition rate has been determined. The internal transition rate has been used to estimate a neutrino capture rate on ⁸¹Br, which yields a log ft of 5.13±0.09 for the reaction ⁸¹Br( ν, e ^-)^81mKr. A new isomer with a half-life of 3.3±0.9 s has been observed in ⁸⁵Nb. The existence of an earlier reported isomer with a half-life of 56 s in ⁸⁶Nb has not been confirmed.     

Isomer shift of the 6.2 keV nuclear transition of 181Ta in Cu3TaSe4

The isomer shift of the 6.2 keV nuclear transition of ¹⁸¹Ta in Cu₃TaSe₄ was investigated by nuclear gamma resonance spectroscopy. Relative to tantalum metal the isomer shift measured corresponds to + 32.64±0.03 mm sec^?1, which is about 17 mm sec^?1 larger than that of the isotypic Cu₃TaS₄. This is explained by the lower electronegativity of selenium as compared to sulphur.     

In-beam study of74Br and a first cascade in75Kr

An in-beam study of⁷⁴Br has been carried out using γ-ray spectroscopy in connection with the reactions (³He,p2in) and (d,2n) on⁷⁴Se targets. Separate level schemes on top of the two β-decaying isomers of⁷⁴Br are proposed. Two cascades connecting highspin states are assigned to populate theI ^π=4⁽⁺⁾ isomer. In this level scheme, the excited states at 72.1, 188.3 and 472.0 keV are found to have half-lives of 13.3, 0.7 and 0.7 ns, respectively. The low-spin isomer of⁷⁴Br is tentatively assigned asI ^π=(0^?). This state is populated by two other cascades. For the low-spin levels two-particle configurations of proton and neutron Nilsson orbitals are proposed. The high-spin states are tentatively interpreted as arising from the configurations (πg _9/2,νg _9/2) and (πg _3/2,νg _9/2). As a by-product, a cascade of four transitions has been observed during the³He bombardment of⁷⁴Se and tentatively assigned to negative-parity states in⁷⁵Kr.     

Relation of contact densities with Mössbauer isomer shifts for 35.46 keV M1 transition of125Te

The internal conversion electron and Mössbauer isomer shifts associated with the 35.46 keV M1 transition of¹²⁵Te were observed for different metal samples into which radioactive¹²⁵I as probe atoms were introduced by means of ion-implantation. From the correlation between the Mössbauer isomer shifts and intensity ratios of O shell to N_I shell conversion electrons, a relation between 5s-electron contact densityp _5s(0) in a.u. and isomer shift δ in mm/s was deduced to bep _5s(0)=106+30.3 δ±4.3[(δ?0.30)²+0.069]^1/2, where δ was measured relative to ZnTe in mm/s. The change of the nuclear charge radius in the 35.46 keV M1 transition of¹²⁵Te was found to be ΔR/R=(0.85±0.12)×10^?4 (corresponding to Δ<r ²>=(3.7±0.5)×10^?3 fm²) when a theoretical 4s-electron contact density of 928 a.u. was used.     

Isomeric states in180Os

Two new isomers have been observed in¹⁸⁰Os. A high-K isomer withI, K ≧20 and a half-life ofT _1/2=12+4 ns have been established. It deexcites via two transitions into the 18⁺ level of the yrare band indicating an unusually smallK-hindrance factor. Evidence for an isomer withI, K>16 and a half-life ofT _1/2=41±10 ns was found. A half-life of 17±3 ns was measured for the previously known 7^? state at 1862 keV. The decay scheme of the previously known 7^? isomer at 1928 keV has been extended and a revised version is presented.     

Thex- (orΔ) transition in152Dy

A 53.3 keV E2 transition de-exciting the 60 ns isomer in¹⁵²Dy has been identified in γγ-coincidence measurements, which locates that isomer at E_x=5088 keV. The half life of the 11^? level at 3161 keV was measured to be T_1/2=4.3±0.9 ns.     

Isomer shift calibration of61Ni by lifetime variation measurements in the electron capture decay of57Ni

In the present work, differential ionization chambers are used in order to measure the difference in the electron capture decay rate of⁵⁷Ni nuclei in several pairs of different chemical compounds. Combination of these values with the corresponding Mössbauer isomer shifts provides a reliable experimental method to determine differences in electron densities at the nucleus. This allows to calibrate the isomer shift scale of the concerned nuclide. By using⁶¹Ni isomer shifts given in the literature, this work leads to the first experimental determination of the⁶¹Ni isomer shift calibration constant α=?(1.8±0.9)·10^?3.a ₀ ³ mm.s^?1. This corresponds to a change in the mean-square charge radius Δ(r ²)=?(7.2±3.4)·10^?4 fm² during the 67.4 keV Mössbauer transition of⁶¹Ni.     

New isomers in83Br,85Rb,85Kr and86Kr

Using methods of in-beam spectroscopy in connection with 35 MeV⁷Li bombardment of⁸²Se targets four new isomers have been identified. They are observed in⁸³Br at 3070 keV (T_1/2=0.6±0.2 μs), in⁸⁵Rb at 2826 keV (T_1/2=12.5±0.6 ns), in⁸⁵Kr at 1991 keV (T_1/2=1.2+ _0.4 ^1.0 μs) and in⁸⁶Kr at 2250 keV (T_1/2=3.1±0.6 ns). Spin and parity 19/2^? have been assigned to the new isomer in⁸⁵Rb that is interpreted as the coupling of a p_3/2 proton to the g ₉ ^2/?2 two-neutron excitation of the N=48 neutron system. Using the TDPAD method an upper limit for the g-factor of ¦g¦≦0.17 has been estimated for this isomer. The same two-neutron excitation is also believed to be responsible for the new isomer in⁸³Br. The new isomers in⁸⁵Kr and⁸⁶Kr are interpreted as configurations containing the two-proton excitation (f ₅ ^2/?1 , p ₃ ^2/?1 ) where in the isomeric 17/2⁺ level of⁸⁵Kr an additional g_9/2 neutron hole is involved.     

Biopolymeric electrolyte based on glycerolized methyl cellulose with NH<Subscript>4</Subscript>Br as proton source and potential application in EDLC

In the present work, biopolymer electrolyte films based on MC doped with NH₄Br salt and plasticized with glycerol were prepared by solution casting method. Fourier transform infrared (FTIR) spectroscopy analysis confirms the interaction between MC, NH₄Br, and glycerol. X-ray diffraction (XRD) explains that the enhancement of conductivity is affected by the degree of crystallinity. This result is verified by field emission scanning electron microscopy (FESEM). For unplasticized system, sample containing 25 wt% of NH₄Br possesses the highest ionic conductivity of (1.89 ± 0.05) × 10^?4 S cm^?1. The addition of 30 wt% glycerol increases the conductivity value up to (1.67 ± 0.04) × 10^?3 S cm^?1. The conduction mechanism was best presented by the correlated barrier hopping (CBH) model. The linear sweep voltammetry (LSV) and cyclic voltammetry (CV) result confirms the suitability of the highest conducting electrolyte to be employed in the fabrication of electrochemical double layer capacitor (EDLC).     

Population of the 236U shape isomer in a photonuclear reaction

A fission isomer with a half-life of 115 ± 5 ns and a yield ratio Y_iso/Y_prompt = (2.02 ± 0.16) × 10^?5 was observed in bremsstrahlung-induced fission of natural uranium. The isomer is ascribed to ²³⁶U populated via a ²³⁸U(γ, 2n) reaction. The integrated cross section for isomeric fission is determined to be σ_int = 32 ± 6 μb MeV. Comparing this value with a calculated total isomer production cross section, a branching ratio of the isomer decay of Γ^γ_II/Γ^f_II ≈ 6 can be deduced.     

Hyperfeinstrukturuntersuchungen an wasserfreien Eisenhalogeniden mit Hilfe des Mössbauereffektes

Mössbauer effect measurements were performed with the anhydrous iron halides FeCl₂, FeBr₂ and FeI₂ at 78° K and 4 K° and with FeCl₃ at 4 °K. The quadrupole splitting, the isomer shift and the magnetic field at the nucleus were determined. From the quadrupole splitting it follows that in FeCl₂, FeBr₂ and FeI₂ the ground state is a doublet and that the singulet in these compounds is separated from it by (145±35) cm^?1, (175±35) cm^?1 and (135±35) cm^?1 respectively. The isomer shift shows the presence of strong covalence effects in all compounds. The large isomer shift in FeBr₂ cannot be fully explained. From the isomer shift and the magnetic field at the nucleus in FeCl₃ it can be concluded that the Fe⁺⁺⁺ ions has an 3d ^5,6 4s ^0,45 configuration. In FeCl₂, FeBr₂ and FeI₂ the smallness of the magnetic field can be explained by a not fully quenched orbital angular momentum of 0.6<L _z<1.     

Calibration of the isomer shift of121Sb and119Sn by means of Mössbauer spectroscopy and molecular orbital calculation

The relationship between the isomer shifts in Mössbauer spectroscopy and the electron contact densities has been investigated for several antimony and tin compounds. Mössbauer spectra for¹²¹Sb in rapidly frozen solutions of antimony compounds were measured. The isomer shifts are compared with the valence electron densities at the antimony nucleus calculated with theab initio molecular orbital method. The relative difference of the nuclear charge radius ΔR/R could be obtained as ΔR/R =?(10.2±1.0)×10^?4 for the 37.15 keV M1 transition of¹²¹Sb. Further, some computations of the electron density at the tin nucleus for several tin compounds were performed. By comparing the valence electron contact densities with isomer shifts, which had been reported for several tin compounds in rare-gas matrix states, the value of ΔR/R for 23.87 keV M1 transition in¹¹⁹Sn was estimated to be (1.57±0.03)×10^?4.     

Static moments of 54Fem and perturbed angular distributions with combined dipole and quadrupole interactions

The static moments of a new I^π = (10⁺) isomer in ⁵⁴Fe (E_x = 6528keV; τ = 525 ± 10ns) were measured by the perturbed angular distribution method with the results g = +0.778 ± 0.010, |Q| = 72 ± 7efm². The isomer was then used to study the combined interaction produced by weak randomly-oriented electric field gradients in the presence of a strong magnetic field.