High-spin states in neutron-rich 102Mo nucleus

High-spin states in neutron-rich 102Mo nucleus have been studied by measuring the prompt γ-rays in the spontaneous fission of 252Cf. The previous level scheme has been updated and some new levels and transitions are identified. The one-phonon γ-band is expanded and a band head level of the two-phonon γ-band is proposed. The systematic characteristics of yrast bands, one-phonon γ-bands, two-phonon γ-bands and quasi-particle bands in 102Mo, 104Mo and 106Mo are discussed.     

Observation of a new rotational band in 104Nb nucleus

The high spin states in neutron-rich 104Nb have been investigated from study of prompt γ-rays in spontaneous fission of 252Cf with the Gammasphere detector array. A new rotational band has been identified for the first time. This band is proposed as a semi-decoupled band based on the configuration π5/2-[303](⊕)v1/2-[541].     

Structure of low-lying quadrupole states in nucleus <Superscript>134</Superscript>Xe

Starting from the Skyrme interaction, we study the M1 transitions between vibration quadrupole states. The finite rank separable approach for quasiparticle random phase approximation is used. As an example, we investigate the properties of the low-energy spectrum of quadrupole excitations in nucleus ¹³⁴Xe.     

Observation of a new rotational band in ~(104)Nb nucleus

The high spin states in neutron-rich 104Nb have been investigated from study of prompt γ-rays in spontaneous fission of 252Cf with the Gammasphere detector array. A new rotational band has been identified for the first time. This band is proposed as a semi-decoupled band based on the configuration π5/2-[303]ν1/2-[541].     

Signature splitting in two quasiparticle rotational bands of <Superscript>180,182</Superscript>Ta

The signature splittings in K^π = 1 ⁺: 7 /2[404] _π?9 /2[624] _ν, K^π = 0^?: 9 /2[514] _π?9 /2[624] _ν bands of ¹⁸⁰Ta and K^π = 0^?: 7 /2[404] _π?7 /2[503] _ν, K^π = 1^?: 5 /2[402] _π?3 /2[512] _ν, K^π = 1⁺: 7 /2[404] _π?9 /2[624] _ν bands of ¹⁸²Ta are analysed within the framework of two-quasiparticle rotor model. The phase as well as magnitude of the experimentally observed signature splitting in K^π = 1⁺ band of ¹⁸⁰Ta, which could not be explained in earlier calculations, is successfully reproduced. The conflict regarding placement of a 12 ⁺ level in K^π = 1 ⁺: 7 /2 ⁺[404] _π?9 /2 ⁺[624] _ν ground-state rotational band of ¹⁸⁰Ta is resolved and tentative nature of K^π = 0^?: 7 /2[404] _π?7 /2[503] _ν, K^π = 1⁺: 7 /2[404] _π?9 /2[624] _ν bands observed in ¹⁸²Ta is confirmed. As a future prediction for experimentalists, these two-quasiparticle structures observed in ¹⁸⁰Ta and ¹⁸²Ta are extended to higher spins.     

Energy spectra and angular distribution of projectile-like fragments in 84 MeV <Superscript>12</Superscript>C + <Superscript>169</Superscript>Tm

Kinetic-energy spectra and angular distribution of projectile-like fragments have been measured in the reaction of 84 MeV ¹²C on ¹⁶⁹Tm, using the surface barrier silicon-based ΔE-E telescopes. The fragments close to the projectile show typical spectra of quasi-elastic transfer reactions, which were found to be in agreement with the calculations based on the direct surface transfer reaction model. A significant cross-section of fast alpha-particles was found at forward angles, reminiscent of incomplete fusion reactions, which could be explained in terms of the direct surface transfer reaction model after taking into account the level density of continuum states in the heavy reaction product. The results have been explained in terms of the continuous evolution of the reaction mechanism as a function of the mass transfer. Received: 13 March 2002 / Accepted: 3 May 2002     

Microscopic study of low-lying yrast spectra and deformation systematics in neutron-rich <Superscript>98–106</Superscript>Sr isotopes

Variation-after-projection (VAP) calculations in conjunction with Hartree-Bogoliubov (HB) ansatz have been carried out for A = 98–106 strontium isotopes. In this framework, the yrast spectra with J ^Π ≥ 10⁺, B(E2) transition probabilities, quadrupole deformation parameter and occupation numbers for various shell model orbits have been obtained. The results of the calculation for yrast spectra give an indication that it is important to include the hexadecapole-hexadecapole component of the two-body interaction for obtaining various nuclear structure quantities in Sr isotopes. Besides this, it is also found that the simultaneous polarization of p _3/2 and f _5/2 proton subshells is a significant factor in making a sizeable contribution to the deformation in neutron-rich Sr isotopes.     

Structure of low-lying <Superscript>12</Superscript>C resonances

The hyperspherical adiabatic expansion is combined with complex scaling and used to calculate low-lying nuclear resonances of ¹²C in the 3α model. We use Ali-Bodmer potentials and compare results for other potentials α-α with similar ⁸Be properties. A three-body potential is used to adjust the ¹²C resonance positions to desired values extending the applicability of the method to many-body systems decaying into three α-particles. For natural choices of three-body potentials we find 14 resonances below the proton separation threshold, i.e. two 0⁺, three 2⁺, two 4⁺, one of each of 1^±, 2^-, 3^±, 4^-, and 6⁺. The partial-wave decomposition of each resonance is calculated as a function of the hyperradius. Strong variation is found from small to large distance. The connection to previous experimental and theoretical results is discussed and agreements as well as disagreements are emphasized.     

Three-body structure of low-lying <Superscript>18</Superscript>Ne states

We investigate to what extent ¹⁸Ne can be descibed as a three-body system made of an inert ¹⁶O core and two protons. We compare to experimental data and occasionally to shell model results. We obtain three-body wave functions with the hyperspherical adiabatic expansion method. We study the spectrum of ¹⁸Ne , the structure of the different states and the predominant transition strengths. Two 0⁺, two 2⁺, and one 4⁺ bound states are found where they are all known experimentally. Also one 3⁺ close to threshold is found and several negative-parity states, 1^-, 3^-, 0^-, 2^-, most of them bound with respect to the ¹⁶O excited 3^- state. The structures are extracted as partial-wave components, as spatial sizes of matter and charge, and as probability distributions. Electromagnetic decay rates are calculated for these states. The dominating decay mode for the bound states is E2 and occasionally also M1 .     

Observation of complete- and incomplete-fusion components in <Superscript>159</Superscript>Tb , <Superscript>169</Superscript>Tm ( <Superscript>16</Superscript>O,x) reactions: Measurement and analysis of forward recoil ranges at E/A ≈ 5-6 MeV

With a view to study complete- and incomplete-fusion components in ¹⁵⁹Tb , ¹⁶⁹Tm ( ¹⁶O , x reactions, experiments have been carried out at the Inter-University Accelerator Center, New Delhi, India using the 15UD Pelletron accelerator facilities. The forward mean recoil ranges for some radio-nuclides; ^168m Lu , ¹⁶⁷Lu , ¹⁶⁷Yb , ¹⁶⁶Tm produced in the ¹⁶O$ + $¹⁵⁹Tb system at ≈ 90 MeV, and ¹⁷⁹Re , ¹⁷⁷Re , ¹⁷⁷W , ¹⁷⁸Ta and ¹⁷⁷Hf produced in the ¹⁶O$ + $¹⁶⁹Tm system at ≈ 87 MeV have been measured. The recoil-catcher activation technique followed by off-line γ -spectrometry has been employed in the present work. The analysis of forward mean ranges for different radio-nuclides has been done in the framework of the degree of linear momentum transfer from projectile to target nucleus by adopting break-up fusion model considerations. Different complete- and incomplete-fusion components, which may be attributed to the fusion of ¹⁶O and/or ¹²C and ⁸Be transfer from the ¹⁶O projectile to the target nucleus have been observed. An attempt has also been made to separate out the relative percentage contributions of complete- and incomplete-fusion components using experimentally measured forward recoil ranges. The complete-fusion contributions deduced from recoil range distribution are found to be consistent with the prediction of the theoretical model code PACE. The analysis of data indicates the complete- and incomplete-fusion competition for both the systems at the given energies.     

A 3-quasiparticle isomer in neutron-rich <Superscript>183</Superscript>Ta

Excited states in neutron-rich ¹⁸³Ta have been studied using a two-neutron transfer reaction of ¹⁸¹Ta(¹⁸O,¹⁶O) . In-beam -rays were measured in coincidence with scattered ions detected by a high-resolution E -E Si telescope for reaction channel selection. Previously known 1-quasiparticle bands are extended to higher spins, and several levels including a T _1/2 = 0.9(3) μs 3-quasiparticle isomer are identified.     

<Superscript>4</Superscript>He<Superscript>3</Superscript>H<Superscript>2</Superscript>H three-body model of the <Superscript>9</Superscript>Be nucleus

Within the framework of the single-channel approximation, an {αtd} model of the ⁹ Be nucleus is presented. A comparative analysis of the t ⁶ Li wave functions describing relative motion of bound states constructed in {ααn} and {αtd} cluster representations is carried out on the example of calculations of the ⁹ Be(γ,t₀)⁶ Li process characteristics. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 85–89, January, 2008.     

Evidence for a K<Superscript>π</Superscript> = 1/2<Superscript>+</Superscript> isomer in neutron-rich <Superscript>185</Superscript>Ta

In this paper we present for the first time the measured delayed neutron (DN) yields and time spectra from high-energy protons interacting with thick ^natPb targets. The 1GeV protons from the accelerator impinged on targets of different thicknesses producing a huge number of spallation-fission products, some of which can be DN precursors. After the beam is switched off, the DNs were detected with optimized ³He counter. The production yields of light DN precursors as ¹⁷N and “usual” fission products as ⁸⁷Br and ⁸⁸Br, which dominate the total DN activity, are obtained both for thin and thick targets. These new data are of great interest for the new generation high-power spallation targets based on liquid-metal technologies. Our findings also should help to constrain the physics models within the simulations codes.     

The study of energy bands in nucleus ~(102)Zr

Theoretical calculations of the energy bands in nucleus 102 Zr are carried out by taking the projected shell model approach, which has reproduced the experimental data. In addition, by analyzing band-head energies, corresponding configurations of yrast band, quasi-particle rotational bands and side bands, we have worked out the microscopic formation mechanism of axially symmetric deformation bands: The low-excitation deformation bands are attributed to the high-j intruder states 1g 7/2 and 1h 11/2 in the N=...     

Description of all observed rotational bands in 128Pr

The configuration-dependent cranked Nilsson-Strutinsky approach was used to investigate the rotational structures in 128Pr and signature splittings of some observed bands could be well described quantitatively at high spin. Its modified model was used to calculate special configurations in order to distinguish the N=4 d3/2s1/2 and g7/2d5/2 orbitals. All observed bands were compared with the calculated configuration assigned to the band and the agreement between experiment and theory is remarkable.     

Low-spin states in <Superscript>182</Superscript>Os and K<Superscript>π</Superscript> = 0<Superscript>+</Superscript>, 2<Superscript>+</Superscript> excited bands

Excited states in ¹⁸²Os were populated by the β⁺/EC decay of ¹⁸²Ir following mass separation. Gamma-ray and conversion electron spectroscopy techniques were employed. Monopole (E0) contributions were determined in transitions populating the ground-state band. A systematic study of the low-spin structures in the Os isotopes is presented and a detailed analysis in the framework of a microscopic configuration mixing approach is performed.     

Investigation of low-lying levels of the <Stack><Subscript>4</Subscript><Superscript>8</Superscript></Stack>Be nucleus in the multiquantum approximation of the orthogonal scheme

In the multiquantum approximation of the orthogonal scheme, specific calculations for the energies and radii of the ₄ ⁸ Be nucleus are performed with allowance for all states characterized by the λ=[44] Young diagram, the quantum numbers K_min and K_min+2 of the O(3(A?1)) group, and the quantum numbers E=K+2N (N≤9) of the U(3(A?1)) group. The convergence of the results with respect to the extension of the basis is studied, and the structure of relevant wave functions is revealed. The results of these calculations are compared with the results obtained in the analogous approximation of the unitary scheme.     

Light-charged-particle emission from hot <Superscript>32</Superscript>S<Superscript>*</Superscript>formed in <Superscript>20</Superscript>Ne + <Superscript>12</Superscript>C reaction

Inclusive energy distributions for light charged particles (p , d , t and have been measured in the ²⁰Ne (158, 170, 180, 200 MeV) + ¹²C reactionsintheangularrange$10^°$ - - $50^°$.Exclusivelight-charged-particleenergydistributionmeasurementswerealsodoneforthesamesystemat158 MeVbombardingenergybyin - planelightchargedparticle - - fragmentcoincidence.Pre - equilibriumcomponentshavebeenseparatedoutfromprotonenergyspectrausingthemovingsourcemodelconsideringtwosources.ThedatahavebeencomparedwiththepredictionsofthestatisticalmodelcodeCASCADE.Ithasbeenobservedthatsignificantdeformationeffectswereneededtobeintroducedinthecompoundnucleusinordertoexplaintheshapeoftheevaporated$d$,$t$energyspectra.Forprotons, evaporatedenergyspectrawereratherinsensitivetonucleardeformation, thoughangulardistributionscouldnotbeexplainedwithoutdeformation.Thedecaysequenceofthehot$³²S$nucleushasbeeninvestigatedthroughexclusivelight - - charged - particlemeasurementsusingthe$²⁰Ne$$(158 MeV) + $¹²C reaction. Information on the sequential decay chain has been extracted through a comparison of the experimental data with the predictions of the statistical model. It is observed from the present analysis that exclusive light-charged-particle data may be used as a powerful tool to probe the decay sequence of hot light compound systems.     

Frequency measurements in the b <Superscript>3</Superscript>Π(0<Subscript>u</Subscript><Superscript>+</Superscript>) - X <Superscript>1</Superscript>Σ<Subscript>g</Subscript><Superscript>+</Superscript> system of K<Subscript>2</Subscript>

Absolute transition frequencies of the b ³Π(0_u ⁺) - X ¹Σ_g ⁺ system of K₂ were measured in a molecular beam with Lamb dip absorption spectroscopy applying a frequency comb from a femtosecond pulsed laser. Both, K atoms and K₂ molecules are present in the beam and are expected to interact by collisions. The atoms can be deflected optically out of the beam, and thus the collision rate between K atoms and K₂ molecules is changed by about an order of magnitude. The molecular transition frequencies for low collisional rate are compared with those for high one. Limits for the collisional frequency shift within the beam are determined.     

Calculation of the Spectroscopic Constants and Strength of the Electron Transition <Emphasis Type="Italic">A</Emphasis>0<Superscript>+</Superscript>-<Emphasis Type="Italic">X</Emphasis><Superscript>1</Superscript>Σ<Superscript>+</Superscript> of the AgAu Molecule

The vibrational, rotational, and centrifugal constants for the electronic states A and X ¹Σ⁺ of the AgAu molecule have been calculated. The calculation is based on the Morse potential functions that were used to approximate the real potential curves of the ground and excited states of AgAu. Using the experimental data on the lifetime of the vibrational levels of the excited electronic state, the strength of the A-X transition was calculated.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 2, pp. 176–180, March–April, 2005