Dipole structures in 122Xe

High-spin levels in ¹²²Xe have been investigated by γ—γ coincidence measurements using the EUROGAMarray. The reaction ⁹⁶Zr(³⁰Si,4n)¹²²Xe at a beam energy of 135 MeV was used. New structures of competing dipole to quadrupole transitions have been observed. Experimental B(M1)/B(E2) ratios have been extracted and compared with theoretical estimates.     

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.     

High-spin states in the neutron rich fission fragments138Xe and139Xe

High-spin structures in the neutron-rich nuclei^138Xe and¹³⁹Xe have been investigated by observing prompt γ -rays from the spontaneous fission of²⁴⁸Cm with the Eurogam spectrometer. The partial level schemes were constructed on the basis of double-, triple- and quadruple-γ coincidences. The ground state band in¹³⁸Xe has been extended up to 5 MeV excitation energy. The structure of the newly observed medium-spin states in¹³⁹Xe is similar to the one of heavier N=85 isotones where vf ₇ ^2/3 , vh_9/2f ₇ ^2/2 and vf ₇ ^2/3 ? 3^? multiplets have been observed.     

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 structure in127Xe and125Xe

Excited states of the nuclei¹²⁷Xe and¹²⁵Xe have been investigated in the inverse kinematic reactions⁴⁸ Ca(⁸² Se,(3.5)n) at 275 MeV beam energy with the OSIRIS multidetector system at the VICKSI-accelerator of the HMI Berlin. The level scheme of¹²⁷Xe was extended up to a level of tentative spin (51/2^?). Two excited bands of 3QP-character were observed. For¹²⁵Xe these structures were extended towards higher spins. Experimental Routhians of selected bands are presented.     

The level scheme of91Nb from the reaction90Zr (p, γ)91Nb

The level scheme of⁹¹Nb has been investigated with the reaction⁹⁰Zr(p, γ)⁹¹Nb. Proton energies between 3.0 and 7.2 MeV were used. The γ spectra were taken with Ge(Li) detectors. Primary γ transitions to 36 excited states of⁹¹Nb up to 3.8 MeV excitation energy and many secondary γ transitions from the decay of those states were observed, leading to an extension of the known level scheme. The proton binding energy for⁹¹Nb was determined as (5167± 5) keV. Eleven γ transitions in⁹⁰Zr, part of them new, from the competing reaction⁹⁰Zr(p, p′ γ) were also observed.     

Possible shape-change observed at high spin in123Cs

The collective moment of inertia ? _band ⁽²⁾ of¹²³Cs produced in the¹¹⁵In+¹²C reaction at 80 MeV has been measured by gamma-gamma energy correlation techniques. The variations of ? _band ⁽²⁾ with the rotational frequency are compared to those of¹²²Xe and analysed in the frame of a cranked Nilsson-Strutinsky model. We conclude that the addition of one proton to the triaxial (γ?30°)¹²²Xe core gives a final prolate-type nucleus¹²³Cs withγ?0° above a rotational frequency?ω?0.55 MeV.     

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     

Transition probabilities and the structure of some negative-parity states in 126,130Xe and 132Ba

The lifetimes of several negative-parity states in ^126,130Xe and ¹³²Ba have been determined by means of the generalized centroid-shift method. The reactions ^124,128Te(α, 2n) and ¹²²Sn(¹³C, 3n) have been used. Following results were obtained: T_1/2(2758 keV) = 1.3 ± 0.2 ns in ¹²⁶Xe, T_1/2 (2060 keV) = 0.20 ± 0.10 ns, T_1/2 (2104 keV) = 0.50 ± 0.10 ns, T_1/2 (2376 keV) = 0.30 ± 0.10 ns and T_1/2 (2973 keV) = 4.6 ± 0.4 ns in ¹³⁰Xe as well as T _1/2(2120 keV) = 0.40 _?0.10 ^+0.20 ns in ¹³²Ba. A systematics of the B(E2; 7 ₁ ^? ? 5 ₁ ^? ) values in the N = 76 nuclei is presented. Electric dipole and quadrupole transition rates are discussed in terms of octupole and quadrupole collectivity. The structure of the 5 ₁ ^? and 7 ₁ ^? states is considered. Nuclear reactions: ^124,128Te(α, 2n), E = 26 MeV, ¹²²Sn (¹³C, 3n), E = 53 MeV; measured E_{gg}, I_{gg}, γ-r.f. Deduced T_1/2, B(σL) in ^126,130Xe and ¹³²Ba. Ge detectors. Generalized centroid-shift analysis.     

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     

The (t, α) reaction on 121Sb and 123Sb

Angular distributions of α-particles from the (t, α) reaction on ¹²¹Sb and ¹²³Sb have been measured for incident tritons of 12 MeV. Levels up to excitation energies of 5.2 and 4.9 MeV in ¹²⁰Sn and ¹²²Sn, respectively, have been identified and analysed by the DWBA. Values of orbital angular momenta of the transferred protons have been assigned and spectroscopic factors deduced for all strongly excited levels. The extracted ground-state wave functions of the target nuclei have been compared with the calculated ones. A mixture of collective degrees of freedom is present in the low-lying states, weakly excited by the above very selective proton pick-up reaction. These states are populated by the pick-up of external protons (outer shells). At higher excitation energy (between 4 and 5 MeV) there are many strongly excited states populated by the proton pick-up from the Z = 50 proton core (inner shells); a predominantly 1p-1h character has been assigned to these states.     

New excited states of the nucleus129Xe

Excited states of¹²⁹Xe have been investigated through the¹²⁶Te(α,n)¹²⁹Xe reaction at the incident energy E=16MeV by means of in-beam gamma ray spectroscopy. Numerous levels below the excitation energy of 2.5MeV were found. Spin assignments were made from side feeding excitation functions. A new level at 274.2keV, which is suggested as spin 9/2 negtive parity bandhead, was observed for the first time.     

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.     

Gamma-gamma energy correlations and moment of inertia in light Xe isotopes

High-spin properties of even ^118–122Xe isotopes have been studied in experiments when a 118 MeV ¹²C beam impinged on ¹¹⁴Cd and ¹¹⁶Cd targets. The γ-rays emitted following the reactions were detected by six NaI(Tl) counters. The coincidence events from the counters were sorted into a two-dimensional matrices, from which the energy-correlation spectra were extracted. From the energy correlation spectra the quantities of the collective moment of inertia $\text{I}$⁽²⁾ are deduced and compared with data obtained for the same nuclei in previous experiments, as well as with results from theoretical studies.     

Identification of High-Spin States in Odd-Odd 126I

Excited states in odd–odd ¹²⁶I have been studied via the heavy–ion induced fusion–evaporation reaction ¹²²Sn(¹¹B,5n2p) at beam energies of 55 and 60 MeV with beams provided by the HI–13 tandem accelerator of CIAE in Beijing.A level scheme consisting of 20 new γ transitions assigned to ¹²⁶I is established.The assignment of the established level scheme to ¹²⁶I is based on the observed coincidences between the newly identified γ–transitions and two previously known cascade γ transitions feeding the ground state of ¹²⁶I, and supported by a cross measurement using the ¹²⁴Sn(^7lI,5n) reaction performed at UTTAC,Japan.The observed structures of ¹²⁶I at high spins show typical properties of collective rotation in a deformed nucleus. their possible configurations are discussed briefly on the basis of knowledge from the neighboring nuclei.     

Investigation of the <Superscript>232</Superscript>Th and <Superscript>238</Superscript>U photofission

The average angular momenta of the ⁸⁴Br, ¹³²Sb, ¹³³Te, and ¹³⁵Xe fission fragments, produced as a result of ²³²Th and ²³⁸U photofission by bremmsstrahlung γ photons with an endpoint energy of 8.5 MeV, have been determined by measuring the isomeric yield ratios. The experimental isomeric yield ratios have been calculated taking into account the contribution from β decay of isobaric nuclei to the yields of isotopes studied.     

Beta-delayed proton emission from heavy nuclei: (I). The observation of coincidences between protons and γ-rays

Coincidences have been detected between γ-rays and β-delayed protons emitted after the decay of very neutron-deficient nuclei. In the three cases studied the decay proceeds to the ground state with branches to the first excited (2⁺) state of the even daughter nucleus of (58±7) % (¹¹⁵Xe to 709 keV in ¹¹⁴Te), (14±3) % (¹¹⁷Xe to 679 keV in ¹¹⁶Te), and (50±10) % (¹⁸¹Hg to 158 keV in ¹⁸⁰Pt). Upper limits of 2 and 6 % can be placed on the branches to the 4⁺ states of ¹¹⁴Te and ¹⁸⁰Pt. For the cases of ^115,117Xe, coincidences with annihilation radiation were also observed; the measured positon/proton ratio determines the difference Q—B_p, between the energy available for electron capture and the proton separation energy for the daughter. For ¹¹⁵Xe the result is 6.20±0.13 MeV, for ¹¹⁷Xe 4.10±0.20 MeV.     

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.     

Der Zerfall des122Xe (T 1/2=20,l h) und des122J (T 1/2=3,6min)

Theγ spectra emitted in the decay of¹²²Xe and¹²²I have been investigated using Ge(Li) detectors and a Ge(Li)-NaI coincidence apparatus. 14γ transitions with energies between 61.8 and 416.9 keV have been identified in the decay of¹²²Xe, 44 transitions between 564.0 and 3,291.0 keV in the decay of¹²²I. Level schemes having 7 excited levels for¹²²I and 21 excited levels for¹²²Te are proposed.     

MICROSTRUCTURE ON COLLECTIVITY IN EVEN 116-122Xe ISOTOPES

Using microscopic interacting boson-fermion model formalism, the ground-band, β-band, γ-band and high spins states in even ^116-122Xe isotopes are successfully described. It can explain the recent experimental result that collective structures may coexist with the single-particle states and subshell feature. It predictes the energies of 1⁺ states.