First observation of yrast band in odd-odd 162Lu

High spin states of the odd-odd ¹⁶²Lu nucleus have been studied via ¹⁴⁷Sm(¹⁹F,4nγ)¹⁶²Lu reaction at 95 MeV beam energy. Level scheme for yrast band based on π[h_11/2]υ[i_13/2] quasiparticle configuration was established up to I^π=(23^?) for the first time. This band shows the signature inversion in energy before backbending generally appeared in this mass region. It is stressed that the signature splitting in ¹⁶²Lu is larger than that in the ¹⁶⁰Tm nucleus.     

First observation of yrast band in odd-odd162Lu

High spin states of the odd-odd¹⁶²Lu nucleus have been studied via¹⁴⁷Sm(¹⁹F,4nγ)¹⁶²Lu reaction at 95 MeV beam energy. Level scheme for yrast band based onπ[h_11/2 v[i_13/2] quasiparticle configuration was established up to I ^π = (23^?) for the first time. This band shows the signature inversion in energy before backbending generally appeared in this mass region. It is stressed that the signature splitting in¹⁶²Lu is larger than that in the¹⁶⁰Tm nucleus.     

Collective Band Structures in Neutron-Rich Odd-A 145,147Ce Nuclei

Through study of the prompt r-rays emitted in the spontaneous fission of ²⁵²Cf, high spin states of neutron-rich odd-A ^145,147Ce nuclei have been investigated. The levels in ¹⁴⁷Ce have been extended. A collective band in ¹⁴⁵Ce have been identified for the first time. The results from the particle rotor model calculations indicate that the yrast bands in ¹⁴⁵Ce and ¹⁴⁷Ce originate from vi_13/2 orbital coupling and the ground states of ¹⁴⁵Ce and ¹⁴⁷Ce originate from (vh_9/2,vf_7/2) and vh_9/2 configiration, respectively. No obvious octupole deformation was observed in these two isotopes, but a side band obtained in ¹⁴⁷Ce may show some octupole correlations.     

Band crossing in 162Dy: Characterisation of negative-parity yrast and yrare sequences

The crossing of an octupole band by a rotation-aligned two-quasiparticle band has been observed in detail in ¹⁶²Dy. Both the yrast and yrare states are identified from the band heads (I =2 and I = 5) to high spin (I ～ 14), with band crossing in both the even-spin and odd-spin sequences.     

New Low-spin Levels in 76Se and Discussion of Its Yrast Band Structure

The decay of bromine–76 was studied using compton–suppressed spectrometer and high–purity ge detectors in singles and coincidence mode, respectively. bromine–76 was produced via two reactions,i. e.,⁷⁵As(α,3n)⁷⁶Br and ⁷⁶Se(p, n)⁷⁶Br.the results of these experiments verified the previously reported levels and gammas of ⁷⁶Se. in addition to the previously described transitions and levels, 39 new γ–rays and 15 new energy levels were found for the first time. spins and parities for new levels are proposed based on the calculated logft values, de–excitation modes of the observed states, and some nuclear reaction experiment results. a new decay scheme of ⁷⁶Br is proposed in the present work. combining with the high–spin states observed by the in–beam γ–ray spectroscopy of a previous decay work, the positive–parity yrast states were compared with the results from calculations in the framework of the projected shell model.     

Study of Multi-Quasiparticle Excited States in 139Ce

High-spin states in ¹³⁹Ce have been populated using the ¹³⁰Te(¹²C,3n) reaction at beam energy of 50MeV. The level scheme of ¹³⁹Ce has been revised and extended greatly up to E=5765.0keV. The level structure of ¹³⁹Ce shows typical characteristics of spherical nucleus, and the high-spin states were formed by the excitations of valence nucleons. Energies of the yrast and near yrast high-spin states in ¹³⁹Ce have been calculated by the empirical shell model, and the multi-quasiparticle nature of high-spin excited states has been discussed.     

High-Spin States and Negative Parity Levels in Neutron-Rich 116,118,120Cd Nuclei

High spin states in neutron-rich ^116,118,120Cd nuclei have been investigated by observing high-fold prompt γ-ray coincidence events from the spontaneous fission of ²⁵²Cf with the Gammasphere detector array. The yrast bands have been extended with spin up to 18h in¹¹⁸Cd and 16h in ^116,120Cd respectively. The band structures are calculated using the cranked shell model and possible origination for the backbends in the yrast bands is discussed. Proposed 5^－ and 7^－ levels are observed in each of these cadmium isotopes, and possible explanation for the negative states is discussed based on systematic comparison. A quasi-rotational band based on 7^－ level in ¹¹⁸Cd has been established.     

Statistical binary decay of35Cl+24Mg at ≈ 8 MeV/nucleon

High spin rotational bands in ¹⁶² Lu and ¹⁶⁴ Lu have been studied through the ¹³⁹ La( ²⁸ Si,5n) and ¹³⁹ La( ²⁹⁽³⁰⁾ Si,4(5)n) reactions respectively. For both nuclei the yrast sequence which is associated with the πh _11/2 ?νi _13/2 configuration shows the signature inversion feature.     

Study of Nuclear Level Structure in Tc Isotopes with Mass A～100

In the present work, the structures of the excited positive/negative-parity yrast states of ¹⁰¹Tc are discussed by using a projected shell model, and a band diagram calculated for the positive-parity yrast band is also shown in order to extract physics out of numerical results. In addition, the analysis of other three bands originated from 3/2^－[301], 5/2^－[303], and 1/2⁺[431] Nilsson states, respectively, is also performed in the framework of this model. Until recently, very little property about the N=52—54 intermediate nuclei in the Z～42—44 region has been known. In order to understand these "transitional nuclei", we select the nucleus ⁹⁵Tc as an example. So in this work, we also present our investigation of the level structure in the ⁹⁵Tc nucleus.     

Lifetimes of triaxial superdeformed states in 163Lu and 164Lu

Lifetimes of states in the yrast superdeformed bands of ¹⁶³Lu and ¹⁶⁴Lu were determined in a Doppler-shift attenuation-method experiment. From fractional Doppler shifts and line shapes, average transition quadrupole moments, Q _t = 8.2_-0.6 ^+1.0 b and 7.1_-0.6 ^+0.5 b, were deduced for one of the bands in ¹⁶³Lu and ¹⁶⁴Lu, respectively. These values are much larger than the quadrupole moment of the normal-deformed yrast band in ¹⁶³Yb, Q _t = 4.9_-0.4 ^+1.3 b, that was also determined in this experiment. Comparison to cranking calculations indicates that both superdeformed bands correspond to a local potential energy minimum with a pronounced triaxiality, γ∼ 20^°. Received: 8 November 2001 / Accepted: 9 January 2002     

Electromagnetic Transition Rates and Deformation Feature in 130Ce

Lifetimes of the excited states in light rare-earth nucleus ¹³⁰Ce have been measured using heavy ion reaction ¹¹⁶Sn(¹⁶O,2n)¹³⁰Ce at beam energy of 73MeV through analyzing the Doppler-broadened line shapes. The reduced transition probabilities B(E2) are extracted from these measurements. The experimental results show that the previously reported anomalously high B(E2) value has not been observed in the present work. The transition quadrupole moment for the yrast band varies with spin and corresponds to a triaxial deformation with γ≈7°.     

Measurement of 125Ba High Spin States

The high spin states of ¹²⁵Ba populated via the ¹⁰⁹Ag(¹⁹F,3n) reaction are measured by using a BGO Compton suppressed HPGe detector array.The negative and positive parity bands built respectively on the h_11/2 and g_7/2 neutron hole states are extended to 35/2^－ and 23/2⁺.Backbending occurs in both signature branches of the negative band at the frequencies close to that of the ¹²⁴Ba yrast band.An onset of backbending in the positive band has been seen.     

A Study for Nuclei 166Hf94—170Hf98 Using Cranking Shell Model with PNC Method

The properties of the band in even nuclei of ¹⁶⁶Hf₉₄—¹⁷⁰Hf₉₈ are investigated using cranking shell model with PNC method. The band crossing frequency, the interaction intensity between yrast and yrare bands, the aligned momentum, and the moment of inertia are calculated. The comparison between the calculation and experimental data shows a good agreement with each other if Lund systematic parameter is used for the Nilsson potential.     

Comparative quadrupole moments of triaxial superdeformed states in 163, 164, 165Lu

Average transition quadrupole moments in the yrast triaxial superdeformed bands of ¹⁶³Lu, ¹⁶⁴Lu and ¹⁶⁵Lu were determined in a Doppler-shift attenuation-method experiment. Fractional Doppler shifts were determined in γ-ray coincidence spectra measured with the Gammasphere array. The transition quadrupole moments derived from these data show a decrease from ¹⁶³Lu to ¹⁶⁵Lu which is not predicted by total-energy surface calculations. Received: 12 August 2002 / Accepted: 23 October 2002 / Published online: 10 December 2002 RID="a" ID="a"e-mail: schoenwa@iskp.uni-bonn.de Communicated by D. Schwalm     

Octupole excitations at high spins in <Emphasis Type="Italic">A</Emphasis> ∼ 160 nuclei

The yrast and yrare states of ¹⁶²Yb are studied within the cranked Nilsson model and random phase approximation. Special attention is paid to the analysis of experimental crossing points between different bands that form the yrast band. We found that, at the rotational frequency ħΩ > 0.3 MeV, there is onset of strong octupole correlations. The results of calculations demonstrate good agreement with available experimental data. The text was submitted by the authors in English.     

Microscopic Mechanism of the ω Variation in Moments of Inertia for the Series of Yrast SD Bands 192—198Pb(1) and 198Po(1)

The variations in moments of inertia (J⁽²⁾ and J⁽¹⁾) with rotational frequency for the series of yrast SD bands in even-even nuclei, ^192—198Pb(1) and ¹⁹⁸Po(1), are investigated by using the particle-number conserving method for treating the pairing interaction (monopole and quadrupole). The observed co variations of J⁽²⁾ and J⁽¹⁾ are reproduced quite well in the PNC calculation, particularly the microscopic mechanism (the contributions from each major shell and each cranked Nilsson orbital) is clearly displayed. It is found that the smooth rise of J⁽²⁾ with ω is attributed to the contribution from the intruder shells (neutron N=7 and proton N=6).     

Doublet bands in 128La and systematic features of energy separationof doublet bands observed in the A～130 mass region

High spin states of ¹²⁸La have been studied through the fusion-evaporation reaction ¹¹⁸Sn(¹⁴N, 4n)¹²⁸La at a beam energy of 69 MeV. A positive-parity side band with the same configuration as that of the yrast band has been identified. Moreover, it is noted that the energy separation ΔE(I)=E(I)_side-E(I)_yrast of all doublet bands reported in odd-odd nuclei in the A～130 mass region exhibit a staggering pattern systematically, and they stagger up at even-spin and stagger down at odd-spin.     

Study for Superdeformed Bands in A～190 Region with Quantum Group Uqp(u2) Model

superdeformed bands in the A～190 region are systematically analyzed by using the twoparameter expansion of quantum group U_qp(u₂) Model. The calculated results of E2 transition γ ray energies are in agreement with experimental data. According to three different methods for the spin assignment of rotational bands, the spin values of the band head I₀ of the yrast SD bands in ¹⁹⁴Hg(1) and ¹⁹⁴Pb(1) are assigned. Furthermore, the physical meaning of the nuclear softness is discussed, and these nuclear softness values of a signature partner are almost equal.     

Low-Lying Spectra and Electromagnetic Transition Rates in 140—162Gd in the Interacting Boson Model

Spectra and electromagnetic transition for the even-even ^140—162Gd isotopes are studied in the framework of the interacting boson model. A schematic Hamiltonian can be used to describe their spectra and transition. The results show that ^140—162Gd are in the transition from the vibrational limit to rotational limit.     

The effect of disorder-induced mode coupling on vibrational spectra of glasses

A theoretical approach based on the Green's function method is proposed for investigation of disorder-induced mode coupling in glasses and of its effect on the intensity of the first order Raman and Infrared spectra. It is shown that while the spectral line widths depend on the Green's function of the glass, dG¢, the mode coupling coefficients depend on dG²¢. The numerical results, obtained in self-consistent approximation for dG¢ and in ladder approximation for dG²¢, demonstrate that the structural disorder leads to strong coupling between modes only if they are of the same type and with close frequencies.