Collective structures and smooth band termination in 109Sn

Six rotational bands up to energies E _x = 24.7 MeV and spins J^π=(79/2^?) have been identified in ¹⁰⁹Sn using the GAMMASPHERE γ-detector array. Four of the bands show smoothly decreasing dynamic moments of inertia at rotational frequencies ?ω > 0.6 MeV. The bands arise at medium spins from a coupling of a valence d_5/2, g_7/2 or h_11/2 neutron to the deformed 2p2h proton excitation of the Z=50 core ¹⁰⁸Sn. At very high ?ω these bands show the typical behaviour of smoothly terminating bands, i.e. a gradual alignment of the angular momenta of the valence particles and holes corresponding to a transition from high collectivity to noncollective states.     

Rotational properties of the odd-Z transfermium nucleus 255Lr by a particle-number-conserving method in the cranked shell model

Experimentally observed ground state band based on the 1/2-[521] Nilsson state and the first exited band based on the 7/2-[514]Nilsson state of the odd-Z nucleus ~(255)Lr are studied by the cranked shell model(CSM) with the paring correlations treated by the particle-number-conserving(PNC) method. This is the first time the detailed theoretical investigations are performed on these rotational bands. Both experimental kinematic and dynamic moments of inertia(J~(1)and J~(2)) versus rotational frequency are reproduced quite well by the PNC-CSM calculations. By comparing the theoretical kinematic moment of inertia J~(1) with the experimental ones extracted from different spin assignments, the spin 17/2~-→13/2~- is assigned to the lowest-lying 196.6(5) ke V transition of the 1/2~-[521] band, and 15/2~-→11/2~- to the 189(1) ke V transition of the 7/2~-[514] band, respectively. The proton N = 7 major shell is included in the calculations. The intruder of the high- j low-? 1 j_((15)/2)(1/2~-[770]) orbital at the high spin leads to band-crossings at ω≈0.20( ω≈0.25) Me V for the 7/2~-[514] α =-1/2(α = +1/2) band, and at ω≈0.175 Me V for the1/2~-[521] α =-1/2 band, respectively. Further investigations show that the band-crossing frequencies are quadrupole deformation dependent.     

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.     

The structure of25Mg

Gamma-decay modes and spin(-parity) assignments of levels in²⁵Mg have been systematically investigated up to 10 MeV excitation energy by particle-γ-ray angularcorrelation measurements with the²⁴Mg(d, pγ) reaction at 6.5 MeV bombarding energy and with the²²Ne(α,nγ) reaction at 11.8, 12.5, 14.4 and 15.5 MeV bombarding energy. A level scheme has been established which is comprehensive up to 8.3 MeV excitation energy forI≦9/2 and up to 10 MeV for 9/2O d _5/2 — 1s _1/2-O d _3/2 shell and the unifieds-d shell Hamiltonian. The agreement is good to excellent. The first intruder states are located near 6.8 MeV excitation energy. The collective properties of²⁵Mg beyond the well established rotational bands are investigated using both the new experimental information and theB(E2)'s obtained from the shell model. The spectrum of²⁵Mg is completely rotational for the first five to six MeV above the yrast line. Shell modelB (M 1)'s reflect the Nilsson model structure of²⁵Mg in great detail. The prospectiveI ^π=9/2^?, 13/2^?, and 15/2^? members of the established negative-parity,K=1/2 band are found in levels atE _x=7801, 9410, and 8896 keV.     

Generalization of multiperipheral model with long range correlations; Van Der Waals approximation

Three enhancements are observed in the final state ω^°π⁺π⁺π⁺⁺π^?π^? selected from the channel $\text{p}\text{p → 3π}{}^{\mathrm{+}}\text{3π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{°}}$ at 715 MeV/c: one in ω^°π^± at 1040 MeV (～ ≈ 55MeV) ω^°π⁺π^?, respectively near 1315 MeV (～ ≈ 100 MeV) and 1405 MeV (～ ≈ 40 MeV). The first two effects are strongly correlated and are interpreted in terms of a sequential decay A^°₂ through a new object, the B₁. The second (ωππ) enhancement seems to be an ?^°?^° effect below threshold and is attributed to a pionic decay of the $\text{K}\text{K}\text{)}{}_{\mathrm{I}}\text{=1}$ effect seen around the same mass in other reactions.     

Excitation of inner hole states in heavy nuclei with the (τ, α) reaction at 205 MeV

Energy spectra have been measured for the (τ, α) reaction at 205 MeV on⁹⁰Zr, ^118,124Sn and ²⁰⁸Pb. Results on the valence neutron shells and on the inner 1f_7/2 shell in ⁹⁰Zr, 1g_9/2 subshell in ^118,124Sn (T_< and T_> components) and 1h_11/2 subshell in ²⁰⁸Pb are presented.     

Particle × phonon multiplets in 65 147 Tb82

High-spin states of¹¹⁵Sb were studied by inbeamγ-ray spectroscopy using the⁸⁹Y (²⁹Si, 2pn) fusionevaporation reaction at a beam energy of 108 MeV. The experiments includedγ-γ coincidence and directional correlation of oriented nuclei (DCO) ratio measurements using six BGO Compton suppressed Ge detectors. An intruderΔJ=2 rotational band has been identified for the first time and it is interpreted as the h_11/2 proton coupled to a two particle-two hole (2p ? 2h) deformed state of the¹¹⁴Sn core. A ΔJ=1 rotational band based on the 2p ? 1h, π{g ₇ ^2/2 ?g ₉ ^2/?1 }, configuration has been extended to the 29/2⁺ state at an excitation energy of 5241 keV.     

Structure of high spin states in83Y

We report on the first in-beam study of high spin levels in⁸³Y which were established up to 9.0 MeV excitation energy and probable spin of 41/2⁺ resp. 27/2^? by means of the reaction⁵⁸Ni(²⁸Si, 3p). Ten lifetimes and six lifetime limits in the 10^?12–10^?9 s range were determined in two recoil distance Doppler shift experiments. The positive parity yrast states form ag _9/2 Coriolis decoupled band with partial alignment, near-rigid rotor moment of inertia and deformationβ ₂=0.29. The negative parity yrast band has very similar collective properties; it shows a pronounced band crossing at rotational frequency ?ω≈0.40 MeV which we associate with twoquasiparticleg _9/2 proton alignment. At 2.56 MeV excitation, a second ΔI=1 band starting with 17/2^? was found. On the basis of the similarity to⁸⁵Y and the very weakE2 decay of this state, we suggest that this band has (3qp) configuration with an alignedg _9/2 neutron pair. The lifetimes of the lowest 2⁺ and 4⁺ state in⁸⁴Zr populated in the reaction⁵⁸Ni (²⁸Si, 2p) were determined to be τ(2)=17.8(11) ps resp. τ(4)=3.5(4) ps.     

In-beam gamma-ray spectroscopy of 116Te

High-spin states of the even-even ¹¹⁶Te were studied by in-beam g-ray spectroscopy using the ¹⁰³Rh (¹⁶O, p2n) fusion-evaporation reaction at a beam energy of 80 MeV. γ-γ coincidence and γ-γ angular correlation analyses were employed for determining the level scheme of ¹¹⁶Te. Levels up to I^π = 27^? and several new states were established. We identified two rotational bands with negative parity, one of which was newly established in the present work. We suggest that such two bands be associated with two proton [(g_7/2) ? (h_11/2)] and two neutron [(d_5/2) ? (h_11/2)] configurations, respectively.     

Two-quasiparticle bands in72Br

High spin states in the doubly odd nucleus⁷²Br were investigated via the reaction⁵⁸Ni(¹⁶O,pn) at 52–65 MeV beam energy. A multi-element detector system consisting of ten Compton supressed Ge detectors (OSIRIS) and two NE213 neutron detectors was used to establish the yrast bands up to 5 MeV excitation energy and probable spins of 15⁺ resp. 14^?. The lifetimes of 12 states and lifetime limits of four states were measured with the recoil distance method, among them four 0.5–3.1 ns isomers. Doppler broadened line shapes obtained in an additionalγγ-coincidence experiment via the reaction⁴⁰Ca(³⁶Ar, 3pn) at 125 MeV revealed further lifetimes and (very short) side feeding times. Three rotational bands were established with deformation parameters ¦β ₂¦≈0.3 and moment of inertia parameters \(\tilde f\) /? ²=36 MeV^?1 (K ^ρ=1^?) resp. 23 MeV^?1; their quasi-particle configurations are being discussed.     

Analysis of the Kω spectrum

We present results of a spin-parity analysis of the Kω system from threshold to 1.52 MeV based on 12 500 events of the type K^?p→K^?π⁺π^?π^op at 7.3 GeV/c. We also present evidence for a possible resonant state decaying into Kω at a mass 1710 ± 15 MeV and width 110 ± 50 MeV.     

The D′ → A′ transition in Br2

A vibrational and rotational analysis is presented for the D′ → A′ transition (2800–2950 Å) of Br₂. The analysis includes 11 rotationally analyzed bands for ⁷⁹Br₂ and 3 for ⁸¹Br₂, plus bandheads for 70 additional v′-v″ bands of ⁷⁹Br₂, ⁸¹Br₂, and ⁷⁹Br⁸¹Br. The latter include some violet-degraded and spikelike features at the long-wavelength end of the spectrum, which are interpreted and assigned with the aid of band profile simulations. The assigned features are fitted directly to 14 vibrational and rotational expansion parameters for the two electronic states, from which the following spectroscopic constants are obtained: ΔT_e = 35706 cm^?1, ω′_e = 150.86 cm^?1, ω″_e = 165.2 cm^?1, B′_e = 0.042515 cm^?1, B″_e = 0.05944 cm^?1, $\text{R′}{}_{\mathrm{e}}\text{= 3.170}\text{A}\text{?}$, $\text{R″}{}_{\mathrm{e}}\text{= 2.681}\text{A}\text{?}$. The spectroscopic parameters are used to calculate RKR potentials and Franck-Condon factors for the transition.     

Shape change and shape coexistence in134Pr

The band structure of doubly odd nucleus¹³⁴Pr has been studied by means of the reaction¹¹⁹Sn(¹⁹F,4n) at 87 MeV bombarding energy. Rotational bands built on πh_11/2?vh_11/2 and πh_7/2?vh_11/2 configurations has been observed. A band consisting of quadrupole transitions, probably involving the vi_13/2[600]1/2⁺ orbital was also weakly populated.     

Systematic behavior ofB(E2) values in the yrast bands of doubly even nuclei

The experimental information onB(E2) transition rates in the yrast bands of doubly even nuclei (126≦A≦184) is systematized. The strength functionS _exp≡B(E2,I→I?2)×E(I→I?2) is found to reveal characteristic behavior significant for structure studies of yrast bands. The energy-weightedB(E2,I→I?2) values (S _exp) and 2?/?²(?: moment of inertia) are plotted versus the rotational frequency squared ?²ω² for each nucleus. In strongly deformed nuclei (N≧90), theS _exp curves smoothly increase for low rotational frequencies suggesting that up to spin valuesI≈8 the ratioQ ₀ ² ? is nearly constant (Q ₀: quadrupole moment). This is not the case in nuclei with a soft core (N≦88). In the relevant discussion, the hydrodynamical model as well as the CAP effect are considered. The results in the backbending region are qualitatively discussed in terms of the two-band crossing model. Evidence is found supporting the prediction of an oscillating behavior of the yrast-yrare interaction.     

Fusion cross section at sub-Coulomb energies

The effective barrier at low energies is approximated by a Coulomb and parabolic barriers. A simple closed formula is obtained for the total reaction cross section which is the natural extension of Wong's results into the low energy domain. Theoretical predictions of averaged energy behaviour agree fairly well with various experimental results. The relation?ω ₀≧π(2kh ²Z₁Z₂ e ²/μ)^1/2 R ₀ ^?3/2 between the curvature and the extremum point of the nucleus-nucleus potential is suggested, based on low energy fusion experiments. By assuming equality sign, it is possible to extract the parameters of the barrier directly from experiment. Incidentally it is found that?ω ₀ remains persistently arround 4.5 MeV for all the reactions which have been investigated.     

Electron scattering from 70Ge and 72Ge

Cross sections have been measured for the elastic and inelastic scattering of electrons from ⁷⁰Ge and ⁷²Ge for momentum transfers from 0.65 to 1.14 fm^?1. Values for the parameters of a Fermi type ground-state charge distribution were obtained from a phase shift analysis of the elastic cross sections. The rms charge radius corresponding to these parameters is 4.07±0.02 fm for ⁷⁰Ge and 4.05±0.03 fm for ⁷²Ge. Using DWBA analysis the reduced transition probabilities for the electroexcitation of the 2₁⁺ and 3₁^? states were found to be: B(E2, ω)↑ = 19.7±1.2, 26.8±2.0 W.u.; B(E3, ω)↑ = 36±5, 37±7 W.u. for ⁷⁰Ge and ⁷²Ge respectively. The J^π = 3^? assignments for the state at 2.562 MeV in ⁷⁰Ge and 2.515 MeV in ⁷²Ge are confirmed.     

High-spin states in26Mg

Theγ-decays of levels in²⁶Mg have been investigated up to 12.5 MeV excitation energy by proton-γ-ray coincidence measurements in the²³Na(α, pγ) reaction at 14.2 and 16 MeV bombarding energy. Lifetime-measurements, made with the Doppler-shift attenuation method, and proton-γ-ray angular-correlation measurements were performed at E_α=14.2 MeV. Many high-spin states were observed, among them levels at 6,978 (5⁺), 7,283(4^?), 7,395(5⁺), 7,953(5^?), 8,202(6⁺), 8,472(6⁺), 9,065(5), 9,112(6⁺), 9,169(6^?), 9,383 (6⁺), 9,542(5), 9,829(7⁺), 9,989(6⁺) and 12,479(8⁺, 7^?) keV excitation energy. The spectrum of positive-parity states and their electromagnetic properties are reproduced with good accuracy by shell-model calculations which employ a unifieds-d shell Hamiltonian and the unrestricted configuration space of the 0d _5/2 1s _1/2 0d _3/2 shell. Members of five inferred rotational bands, withK ^π=0⁺, 2⁺, 3⁺, 0⁺ and 3^? have been observed up to at leastI=6. TheK ^π=2⁺ band shows strong anomalies of excitation energies andE2 transition rates near theI=6 state. The static intrinsic quadrupole moments calculated from the shell model wave functions indicate transitions from prolate to oblate deformation within theK ^π=2⁺ band and also the ground state band. The lowest lyingI ^π=4⁺ state appears to be “spherical” and cannot be associated with a rotational band.     

Valence and inner proton hole states in119in via the (d,3He) reaction

Proton holes states have been studied up toE _x=17 MeV andE _x=3.5 MeV in the¹¹⁹In nucleus via the¹²⁰Sn(d,³He)¹¹⁹In reaction respectively atE _d=108.4 MeV andE _d=51 MeV. DWBA analysis of angular distributions has allowedl attributions for a large number of new levels and the determination of valence and inner hole strength distributions. The first 1g _9/2, 2p _1/2 and 2p _3/2 levels only exhaust 40%, 60% and 32% of their respective sum rule limits. The missing strengths are shared among several low lying levels and significant higher lying contributions. The 1f strength, not identified in the previous experiments is spread fromE _x=1 MeV to about 17 MeV. The low lying levels aroundE _x=2.4 MeV could exhaust some 40% of the 1f _5/2 sum rule. The higher lying strength with a flat maximum aroundE _x=7.5 MeV could account for the 1f _7/2inner hole strength and the missing 1f _5/2 valence strength. The experimental strength functions compare rather well with the predictions of the quasiparticle-phonon model.     

Observations on the electronic spectrum of gaseous FeO

About 400 lines are assigned to FeO emission bands in the region 5580 to 6265 Å. The lower state of all the bands analyzed is identified as the ground state of the molecule, for the value of the lower-state vibration frequency (ω_e = 880.61 ± 0.02 cm^?1) is in excellent agreement with that observed in low-temperature matrix isolation, itself confirmed by isotopic substitution. This state is also observed as the lower state in laser-induced fluorescence. However, 880 cm^?1 is significantly smaller than the value found in laser photodetachment studies of FeO^? (970 ± 60 cm^?1). The rotational analysis is consistent with a parallel transition, ΔΛ = 0, but the value of Λ is not determined. According to theoretical calculations, the orange bands most probably arise from a ⁵Σ-⁵Σ transition. There is at least one nearby excited state, for all analyzed upper levels are perturbed.