Study of superdeformed bands in nuclei withA ∼ 150 by heavy-ion-γ coincidences

Superdeformed (SD) bands in¹⁵²Dy,¹⁵¹Dy and¹⁵¹Tb have been populated via the 5n, 6n and 5np evaporation channels, respectively, with the³³S+¹²⁴Sn reaction at 160 and 170 MeV bombarding energies. Population intensities are in good agreement with existing data for SD bands in^{151, 152}Dy and SD yrast band in¹⁵¹Tb. The excited twin SD band in¹⁵¹Tb with the same-transitions as the band in¹⁵²Dy is populated about 5 times more strongly than by the 6n evaporation channel. This might be explained in terms of competition between proton and emission out of an intermediate, excited superdeformed configuration of¹⁵²Dy.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

First observation of the ν9/2[404] orbital in the A ∼ 100 mass region

A new band, populated by the spontaneous fission of ²⁴⁸Cm and studied by means of prompt γ-ray spectroscopy using the EUROGAM2 array, was observed in ⁹⁹Zr. The 1038.8 keV band head with a half-life T _1/2 = 54(10) ns is interpreted as a K-isomer, corresponding to the 9/2[404] neutron-hole excitation. It is the first observation of this orbital in the mass A ∼ 100 region. The quadrupole moment, Q ₀ = 3.9(3) eb deduced for the new band indicates a large deformation of β = 0.41, which is produced by a specific shape-coexistence mechanism, known in other regions and now found in the A ∼ 100 nuclei. Received: 11 September 2002 / Accepted: 31 October 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: urban@fuw.edu.pl Communicated by D. Schwalm     

Nuclear triaxiality in the A ∼ 160–170 mass region: the story so far

Research in nuclear triaxial deformation has revealed many exciting facts and figures over the last one and a half-decades. Although wobbling motion of nuclei was experimentally discovered at the beginning of the last decade, after almost 25 years of its prediction by Bohr and Mottelson, efforts are still being put to understand this rare nuclear phenomenon in greater detail. The concept of transverse wobbling is one such recent attempt which successfully explains the evolution of experimentally observed wobbling frequency with spin. The population of triaxial strongly deformed (TSD) bands in the A ～160–170 region is favoured for which neutron number (N=92 or 94) is a topic of current debate. Experimental efforts are being put following Bengtsson’s calculations which indicate that the elevated yrast lines for N=92 isotones favour TSD population. In A ～170 mass region, the ambiguity over the real character of certain strongly deformed bands has recently been removed by extensive experimental and theoretical efforts, and the bands have now been firmly established as either enhanced deformed (ED) or superdeformed (SD).     

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 △E(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.     

Description of the Superdeformed Bands of Double Odd Nuclei in A ～ 190 Region

With the supersymmetry scheme including many-body interactions and aperturbation possessing the SO(5)(or SU(5)) symmetry on the rotational symmetry, the superdeformed bands and △I＝4 bifurcation of odd-odd nuclei in A ～ 190 mass region are investigated systematically. Good results for the γ-ray energies, the dynamical moments of inertia, and energy differences △Eγ - △Eref γ are obtained. It shows that this approach is quite powerful in describing odd-odd nuclei in the region.     

Description of the Superdeformed Bands in A～190 Region with a Three-Parameter Formula

The q-deformed moment of inertia, formulated by was first introduced as the mechanical moment of inertia of superdeformed (SD) nuclei. The E2 transition γ-ray energies and the dynamical moment of inertia of the lowest-formed bands in Hg, Ph, and TI isotopes are calculated. The calculated results indicate that the SD bands may be described by the ided-rotor with the q-deformed mpment of inertia.     

Analysis of the threshold anomaly in proton elastic scattering on A ∼- 30 mass nuclei

The threshold anomaly in energy-averaged excitation functions of proton elastic scattering on A ∼- 30 mass nuclei is analyzed in the framework of the Lane model for p-wave threshold effects. A quantitative correlation between the strength of the threshold anomaly and the 2p-wave neutron strength function is reported.     

New multi-phonon gamma vibrational bands in A∼110 neutron-rich nuclei

The high spin states of neutron-rich ¹⁰³Nb, ¹⁰⁷Tc and ¹⁰⁹Tc nuclei in A～110 region have been investigated by measuring prompt γ-γ-γ coincident measurements populated with the spontaneous fission of ²⁵²Cf with the Gammasphere detector array. In ¹⁰³Nb, one-phonon K = 9/2 and two-phonon K = 13/2 γ-vibrational bands have been identified. In ¹⁰⁷Tc and ¹⁰⁹Tc, one-phonon K = 11/2 and two-phonon K = 15/2 γ-vibrational bands, in which the zero-phonon bands are based on K=7/2 excited states, have also been identified. The two-phonon bands are first observed in odd-Z nuclei. The characteristics for these band structures have been discussed.     

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.     

πg9/2(⊕)vh11/2 doublet bands in A～100 mass region

Using the model with one particle and one hole coupled with a triaxial rotor, the πg(-1)(9/2)(⊕)vh11/2 doublet bands in the A ～ 100 mass region are studied, and compared with the πh11/2(⊕)vh(-1)(11/2) doublet bands.It is found that the calculated results for the configuration of πg(-1)(9/2)(⊕)vh11/2 are very similar the results for a pure h11/2 proton particle and a neutron quasiparticle with λn =ε5. After including the pair correlation, the model describes the candidate chiral doublet bands in 106Rh successfully, which supports the interpretation of chirality geometry.     

Searching for high-K isomers in the proton-rich A～80 mass region

Configuration-constrained potential-energy-surface calculations have been performed to investigate the K isomerism in the proton-rich A～ 80 mass region. An abundance of high-K states are predicted. These high-K states arise from two and four-quasi-particle excitations, with K~π= 8~+ and K~π= 16~+, respectively. Their excitation energies are comparatively low, making them good candidates for long-lived isomers. Since most nuclei under study are prolate spheroids in their ground states, the oblate shapes of the predicted high-K states may indicate a combination of K isomerism and shape isomerism.     

Use of the kramers — kronig method for analyzing internal reflection spectra in the region of strong infrared bands

Journal of Applied Spectroscopy -     

The ν9/2[404] orbital and the deformation in the A ∼ 100 region

A T _1/2 = 16(2)ns isomeric level, populated in the spontaneous fission of ²⁴⁸Cm, has been found in ¹⁰¹Zr at 941.8keV in a measurement of prompt -rays using the EUROGAM2 array. The level is interpreted as a K-isomer corresponding to the 9/2[404] neutron-hole excitation. The quadrupole moment, Q ₀ = 3.6(4)eb, deduced for the new band indicates a large deformation of , which is produced by a specific shape-coexistence mechanism. This is another observation of the 9/2[404] orbital in the mass region, confirming the presence of the effect reported first in our previous work. The 9/2[404] neutron-hole excitation is also confirmed in the ⁹⁷Sr nucleus and the deformation is determined for this configuration. The properties of the 9/2[404] neutron orbital and its influence on the onset of deformation in the region are discussed.PACS: 23.20.Lv transitions and level energies - 21.60.Cs Shell model - 25.85.Ca Spontaneous fission - 27.60. + j      

Description of the Superdeformed Bands of the Odd-Odd Nuclei in A～150 Region

With the supersymmetry scheme including many-body interactions, the global property and the ΔI=4 bifurcation in the superdeformed (SD) bands of odd-odd nuclei in A～150 mass region are investigated systematically. Good results for the γ-ray energies, the dynamical moments of inertia, and energy differences ΔE_γ-ΔE_γ^ref are obtained. It shows that this approach is quite powerful in describing not only the SD bands in even-even and odd-A nuclei but also those in odd-odd nuclei in the mass region.     

Intense spontaneous amplified emission of Li2 diffuse violet bands in the 4400 Å region

We report observation of intense spontaneous amplified radiation of Li₂ diffuse violet band in the 4100–4900 Å region. The radiation is strongly enhanced when the lithium vapor in a heat pipe is optically pumped with a pulsed dye laser with the output wavelength tuned to near the Li 2s–4s two-photon resonance transition. The diffuse violet band can probably be assigned to a recently reported triplet bound-free (2³ _g a ³ _u ⁺ ) transition. It is found that the productions of the molecular diffuse band are contributed from Li atoms as well as Li₂ molecules. The excitation functions and their dependence on laser power density are presented and the mechanisms for producing the diffuse bands are discussed.Department of Physics, National Central University, Chung-Li, Taiwan, Republic of Chinabl]References     

Description of the Superdeformed Bands of the Odd-Odd Nuclei in A ～ 150 Region

With the supersymmetry scheme including many-body interactions, the global property and the △I ＝ 4bifurcation in the superdeformed (SD) bands of odd-odd nuclei in A ～ 150 mass region are investigated systematically.Good results for the γ-ray energies, the dynamical moments of inertia, and energy differences △ Eγ - △ Erefγ are obtained.It shows that this approach is quite powerful in describing not only the SD bands in even-even and odd-A nuclei butalso those in odd-odd nuclei in the mass region.     

Observations of “pairing-free” Kπ = 1+ rotational bands in deformed odd-odd A ∼ 100 nuclei

Rotational bands with K^π = 1⁺ in the odd-odd nuclei ^100,102₃₉Y and ^102,104₄₁Nb are postulated from β⁻ decay of t heir even-even parents. Each two-quasiparticle band has a moment of inertia very close to that of a rigid spheroidal nucleus with deformation β ∼ 0.3, hence these bands are nearly “pairing free”.     

A high-resolution study of the ν3 and 2ν80 bands of propyne

The ν₃ and 2ν₈⁰ parallel bands of propyne (methyl acetylene) at 2137.88 and 2066.33 cm⁻¹ have been studied at 0.006 cm⁻¹ resolution. Their Fermi resonance and interaction with the ν₈ + 2ν₉, ν₇ + ν₉, and ν₈ + ν₉ + ν₁₀ levels have been investigated. Molecular constants were determined from the assignment of 1150 lines. However, the rms error of 0.0028 cm⁻¹ showed the presence of additional perturbations which cannot be uniquely identified.