Der Zerfall des125m Xe,des127m Xe und des127g Xe

The decay of^125m Xe produced by the reaction¹²²Te(α, n)^125m Xe using a target enriched in¹²²Te (95.4%) and the decay of^127m Xe produced by the reaction¹²⁷J(d, 2n)^127m Xe have been investigated: ^125m Xe decays with a half-life ofT _1/2=(56±3) sec by ayy- cascade withE _γ1=(140.4 ±0.5) keV andE _γ2=(110.5 ±0.5) keV. The experimental conversion coefficients yield multipolarities ofE3 for the 140.4 keV isomeric transition and predominantlyM1 for the 110.5 keV-transition. ^127m Xe decays with a half-life ofT _1/2=(71±2) sec. The decay also proceeds by aγγ-cascade with an isomeric E3 transition ofE _γ1=(172.5±0.3) keV and a predominantlyM1 transition ofE _γ2=(124.6±0.3) keV. In the decay of^127g Xe an additional branching of the electron capture to a level at (618.1±0.3) keV was observed. The relative probability forK-captureP _K618/P_K375=0.40 ±0.07 yields a total transition energyQ _EC=(664 ±4)keV. A spin of 1/2⁺ was assigned to the ground state.     

In-beam study of127Xe

The level structure of the¹²⁷Xe nucleus has been studied through the¹²⁵Te(α, 2n)¹²⁷Xe reaction atE _α=27 MeV by in-beamγ-ray spectroscopic methods including three-parameterγ-γ-t coincidences, angular distribution and linear polarization as well as lifetime measurements. The results supplemented current information and, in particular, established the existence of a new isomeric state having a half-life of 25±3 ns.     

Band structure on the low-j orbitals in the nucleus125Xe

In¹²⁵Xe eight lowlying band structures of positive parity were established via the¹²²Te(α, n) reaction by means of in-beamγ-ray spectroscopy using a setup of 6 compton suppressed germanium detectors. The systematics of the related quasi- ′s′_1/2, ′d′_3/2, and ′g′_7/2 bands with the variation of the fermi level in the triaxially deformed region from¹²⁵Xe to¹²⁹Xe is discussed.     

High spin states in120Xe

High spin states in ¹²⁰Xe, populated via¹⁰⁷Ag(¹⁶O, p2n) and¹⁰⁸Pd(¹⁶O, 4n)reactions have been studied using γ-ray spectroscopic techniques. 21 new transitions have been added to extend the level scheme. Two S-bands are extended upto 26⁺ and 22⁺;these bands are found to cross the g. s band at hΩ=0. 39 and 0. 47 MeV. The band structures have been discussed within the framework of CSM.     

The g-factors of isomeric states in127, 128Xe

Excited states in^{127, 128}Xe were populated in the reaction⁹Be+¹²²Sn atE _lab=38 MeV. The de-excitation of the isomeric states 7/2⁺ in¹²⁷Xe and 8^? in¹²⁸Xe was studied using angular distribution and TDPAD methods on molten¹²²Sn targets. The results are $$\begin{gathered} T_{1/2} (7/2^ + ) = 37 \pm 1 ns, g(7/2^ + ) = + 0.241 \pm 0.009 \hfill \\ T_{1/2} (8^ - ) = 83 \pm 2 ns, g(8^ - ) = - 0.036 \pm 0.009. \hfill \\ \end{gathered}$$ The experimentalg-factors suggest the main configurationsvg _7/2 andvh _11/2 g _7/2 for the isomeric states. Detailed analysis of the combined information fromg-factors and transition rates set stringent limits on the admixtures of the wave functions. The quasirotational bands built on the two-quasiparticle 6^? and 10⁺ states are extended to higher spins, (14^?) and (16⁺), respectively, and their structures are analyzed within the framework of the Interacting Boson Model.     

The origin of the background radioactive isotope <Superscript>127</Superscript>Xe in the sample of Xe enriched in <Superscript>124</Superscript>Xe

The results of investigation of ¹²⁷Xe radioactive isotope production in the xenon sample enriched in ¹²⁴Xe, ¹²⁶Xe, ¹²⁸Xe are presented. The isotope is supposed to be the source of the background events in the low-background experiment on search for 2K-capture of ¹²⁴Xe. In this work we consider two channels of ¹²⁷Xe production: the neutron knock-out from ¹²⁸Xe nucleus by cosmogenic muons and the neutron capture by ¹²⁶Xe nucleus. For the first channel the upper limit of the cross section of ¹²⁷Xe production was found to be σ ≤ 0.007 × 10^?24 cm² at 95% C.L. For the second channel the value obtained for the cross section was found to be equal to σ = (2.74 ± 0.4) × 10^?24 cm², which coincides well, within the statistical error, with reference value.     

Study of the124Xe and126Xe structure

The level structure of¹²⁴Xe and¹²⁶Xe is studied on the basis ofβ ⁺ decay of¹²⁴Cs and¹²⁶Cs. The Cs isotopes were produced in the Xe(p, n) Cs reactions at a proton energy ofE≈9.5 MeV. Decay schemes are proposed for these nuclei. The available experimental data are compared with the predictions of various models.     

Study of122–130Xe with the extended interacting-boson approximation

Calculations on the basis of the extended interacting-boson approximation have been made for the positive-parity states of^122–130Xe. The results of the calculations are compared with their energy levels, expecially the backbendings in the yrast bands, and with reducedE2 transition probabilities andg-factors. They are also compared with the staggerings in theγ-vibrational quasibands. The present calculations reproduce the experimental data concerning^122–130Xe.     

High-spin bands in117,119I and118Xe

Excited states in¹¹⁷I,¹¹⁸Xe and¹¹⁹I were populated in the reactions¹⁰⁶Pd+¹⁶O and^{108, 110}Cd+¹²C. The groundstate band in¹¹⁸Xe was observed to its (18⁺) member and the 11/2^? bands in¹¹⁷I and¹¹⁹I to their (35/2^?) and (43/2^?) members, respectively. The structure of the bands in the I isotopes is interpreted as aπ h _11/2 proton coupled to an even-even band structure in Xe, and the band crossings observed in¹¹⁸Xe and¹¹⁹I are interpreted in the Cranked Shell Model framework asAB _n ofv h _11/2.     

In-beam spectroscopy of 120Xe

Excited states of ¹²⁰Xe have been studied by in-beam γ-ray spectroscopy using the ¹¹⁰Cd(¹³C, 3n) and ¹¹¹Cd(¹²C, 3n) reactions. The yrast band was observed up to the 14⁺ level, showing backbending at the 12⁺ state. A γ-band and two new negative-parity bands were found. The low-lying levels of ¹²⁰Xe could be described by the IBA-1 hamiltonian plus a triaxial degree of freedom.     

New in-beam data on125Xe and reinterpretation of negative-parity levels in odd-A neutron deficient Xe isotopes

In-beam data have been obtained on¹²⁵Xe produced in the¹²⁴Te(α, 3n) reaction and have led to new experimental results on theh _11/2 band structure in contradiction with earlier works. From these results, the negative-parity levels known in the odd-A ^123–133Xe isotopes are reinterpreted in the frame of the triaxial rotor model.     

High spin structures of 122Xe

High — spin states in ¹²²Xe have been investigated by γ ? γ coincidence measurements using the EUROGAM array. The reaction ⁹⁶Zr(³⁰Si,4n)¹²²Xe at a beam energy of 135 MeV was used to populate states of ¹²²Xe. The level scheme has been extended up to ～ 13.5 MeV and also enriched as compared to previous studies. New structures of competing dipole to quadrupole transitions have been observed. Experimental B(M1)/B(E2) ratios have been extracted for these structures and compared with theoretical estimates. They have also been compared with similar structures in Xe, Ba and Ce nuclei.     

Transition to non-collective states at high spin in 124Xe

Excited states in ¹²⁴Xe were populated in the reaction ⁸²Se(⁴⁸Ca, 6n)¹²⁴Xe and γ -ray coincidence relationships were measured with the Gammasphere spectrometer. Two new bands are observed and several of the previously known bands are extended in the high- as well as in the low-spin region. Two irregular high-spin structures are also added. The irregularities are a fingerprint of a transition from collective to non-collective behaviour. Configuration assignments to the new structures are proposed on the basis of systematics and by comparing experimental properties with calculations within the framework of the cranking model.     

Thermal neutron induced charged particle reactions in radioactive targets of37Ar,109Cd,125Xe,127Xe,and132Cs

Thermal neutron induced charged particle reactions in a radioactive target of³⁷Ar have been studied. Upper limits of the cross-sections for the (n, α) reaction in radioactive targets of¹⁰⁹Cd,^{125, 127}Xe, and¹³²Cs have been obtained. The isotopically pure targets were produced at the ISOLDE facility at CERN and irradiated with thermal neutrons at the high flux reactor of the Institute Laue-Langevin in Grenoble. Charged particles from (n, p) and (n, α) reactions in³⁷Ar were observed with cross-sections of 69±14b and 1970 ±330b, respectively. TheQ-values for these reactions were determined to be 1600 ±12 keV and 4630±7 keV, in agreement with existing mass data. The branching ratio Γ_α/Γ_p of the³⁷Ar capturing state was found to be 28.5±2.7. An upper limit of the cross-section for the (n, γα) reaction in³⁷Ar was obtained.     

High spin states in126Xe

High spin states of¹²⁶Xe have been populated by means of the¹¹⁶Cd(¹³C, 3n) reaction using the OSIRIS-12 detector system. A level scheme consisting of 13 bands has been established. More than 40 new levels were observed and several spin and parity assignments could be made. Experimental Routhians and alignments of selected bands are presented.     

Yrare bands of 121Xe

High-spin states in ¹²¹Xe have been studied via the ¹⁰⁹Ag (16O, p3n) ¹²¹Xe reaction at a beam energy of 80 MeV. Several rotational bands based on one- and three-quasiparticle excitations have been established. Among them, an unfavoured yrare rotational band with unfavoured signature has been newly identified. Received: 19 November 1998     

Signature inversion in the yrare band of <Superscript>119</Superscript>Xe

Excited states of the ¹¹⁹Xe nucleus have been studied by using in-beam γ-ray spectroscopy with the ¹⁰⁷Ag ( ¹⁶O, p3n) ¹¹⁹Xe fusion-evaporation reaction at a beam energy of 85 MeV. The level scheme of ¹¹⁹Xe has been derived from γ-γ coincidence and γ-γ angular correlation analyses. We have, for the first time, established the second negative-parity favored and unfavored states built on the 11/2^- state, namely the yrare rotational bands in ¹¹⁹Xe. In contrast to the behavior of the yrast bands where the favored states are lying lower in energy, the yrare favored states were observed to lie above the unfavored band. Such a signature inversion in ¹¹⁹Xe is changed to be normal at I = 12?. Received: 8 January 2002 / Accepted: 18 April 2002     

Sub-Coulomb transfer and fission in collisions of129Xe,132Xe and136Xe with238U

Integral cross sections for fission and for one- and two-neutron transfer reactions in the system¹³²Xe+²³⁸U were measured radiochemically in the energy range 0.7≦E/E _Coul≦1. The excitation functions for fission and transfer are found to be essentially parallel below 0.85×E _Coul. Even at the lowest energies the transfer cross sections exceed the fission cross section by more than one order of magnitude. With the other projectiles¹²⁹Xe and¹³⁶Xe different transfer cross sections illustrating their sensitivity for the ground stateQ-values,Q _gg , are observed while the fission cross sections are the same as in the¹³²Xe +²³⁸U reaction. The fission data are interpreted in terms of a continuous transition between Coulomb fission and several transfer-induced fission processes.     

Band structure of118Xe

High spin states of¹¹⁸Xe have been investigated by means of γ ray spectroscopy using the⁹²Mo(²⁹Si,2pn) at a bombarding energy of 110 MeV. Several new side bands as well as the yrast band were established. A band crossing between the ground state and super bands was observed at ?ω_c = 0.39 MeV. A negative parity band with two quasi particle excitation, and a quasi γ band were also identified.     

Angular correlation measurements in solid Xe sources

A new value has been obtained for the perturbed angular correlation (PAC) in solid ¹²⁷Xe sources while measuring the temperature dependence of the 172–203 keV AC in ¹²⁷I by means of a thermostat.