The E → B transition (3000–3140 Å) in Br2

The region 3030–3140 Å of the emission spectrum of Br₂ is reinvestigated using sources containing separated ⁷⁹Br₂ and ⁸¹Br₂. The analysis, which spans v′ levels 0–15 and v″ levels 8–31, indicates that the transition in this region is the analog of the E → B system in I₂, and it is so redesignated. The following spectroscopic constants are obtained for the E state of ⁷⁹Br₂: T_e = 49 779.06 cm^?1, ω_e = 150.46 cm^?1, ω_eχ_e = 0.383 cm^?1, B_e = 0.04172 cm^?1, $\text{R}{}_{\mathrm{e}}\text{= 3.20}\text{A}\text{?}$.     

Measurement of the quadrupole moments of the first 2+ states of 130Ba and 134Ba

The quadrupole moments of the first 2⁺ states of ^130,134Ba were measured using the reorientation precession technique. Prolate deformations were determined for both nuclei. The quadrupole moments found were Q = ?0.33 ± 0.24 b and ?0.31 ± 0.24 b for ¹³⁰Ba and ¹³⁴Ba, respectively.     

Systematic study of the product((E(2_2~+)/E(2_1~+)) * B(E2)↑) through the asymmetric rotor model

A systematic study of the product((E(2_2~+)/E(2_1~+))*B(E2)↑) is carried out in the major shell space Z=50-82,N=82-126 within the framework of the asymmetric rotor model where the asymmetry parameter γ0reflects change in the nuclear structure.A systematic study of the product((E(2+)/E(2+))*B(E2)↑) with neutron number N is also discussed.The product((E(2_2~+)/E(2_1~+))*B(E2)↑) provides a direct correlation with the asymmetry parameter γ0.The effect of subshells is visible in Ba-Gd nuclei with N 82,but not in Hf-Pt nuclei with N 104.We study,for the first time,the dependency of the product((E(2_2~+)/E(2_1~+))*B(E2)↑) on the asymmetry parameterγ0.     

A study of the 138Ba(d,p)139Ba reaction at 19 MeV

The ¹³⁸Ba(d,p) reaction has been studied at an incident deuteron energy of 19 MeV, using the injector-tandem accelerator and the multichannel magnetic spectrograph of the University of Oxford. Deuteron and proton optical model parameters have been obtained from the analysis of elastic scattering experiments on a ¹³⁸Ba target. The parameters have been used to calculate theoretical (d, p) angular distributions on the basis of the DWBA. From the comparison of experimental and theoretical distributions, orbital angular momentum transfers have been deduced and spectroscopic factors determined for all the levels observed up to an excitation energy of 2.5 MeV in ¹³⁹Ba. The spectroscopic information thus obtained is more complete than that from previous studies, and is in satisfactory agreement with expected sum rule limits. A notable item of new information is the assignment of an l_n = 6 transition to the level at 1.54 MeV in ¹³⁹Ba.     

130Ba中的集体运动

为探索原子核中的集体运动,一项在意大利Legnaro实验室XTU串列加速器上开展的在束${\rm{\gamma }}$谱学实验研究大幅拓展了130Ba的能级结构。实验以能量为65 MeV的13C束流轰击120Sn薄靶,布居130Ba的激发态。从激发态退激的${\rm{\gamma }}$射线由GALILEO阵列探测,而与之关联的蒸发粒子由带电粒子阵列EUCLIDES和中子墙NWALL探测。分析符合数据鉴别了一系列新的转动带,其中一部分布居9.4 ms同核异能态。结合已知的电四极矩和磁矩信息,提取了该同核异能态的g因子。分析多条转动带,发现130Ba可能处于长椭形变,也可能处于扁椭形变,而其集体转动方向可能沿主轴,也可能沿主轴以外的倾斜方向。这是首次在130核区发现沿倾斜方向的集体转动。理论分析建议将部分新发现的结构解释为基于二准粒子组态的摇摆运动,这是实验上在偶偶核中观测到的首例基于两准粒子组态的摇摆带结构。     

A measurement of B(E3;0+ → 31−) and some E2 transition probabilities in 132, 134, 136, 138Ba using Coulomb excitation

Reduced transition probabilities, B(E2) and B(E3), have been measured for low-lying 2⁺ and 3^? states in ^{132, 134, 136, 138}Ba using Coulomb excitation by 40 MeV ¹²C ions. The B(E2) values are in general consistent with previous measurements and the B(E3;0⁺ → 3₁^?) values are 0.176 ± 0.022, 0.148 ± 0.018, 0.155 ± 0.018 and 0.133 ± 0.013 e² · b³ for ^{132, 134, 136, 138}Ba respectively. These B(E3) values correspond to about 24 to 17 W.u. and such enhancements suggest that these 3^? states have an essentially collective character which may be attributed to octupole vibrations.     

Isotope Shifts in the TiO B-X (1-0) Band

The absorption spectrum of the B³Π-X³Δ (1-0) band of the TiO molecule has been studied at sub-Doppler resolution by crossing an effusive beam of TiO with a cw tunable laser beam and by collecting the induced fluorescence light. The five bands involving the ⁴⁶Ti, ⁴⁷Ti, ⁴⁸Ti, ⁴⁹Ti, and ⁵⁰Ti isotopic species have been observed and interpreted. A simultaneous analysis of the five isotopic data leads to accurate molecular constants and energy levels for the B³Π electronic state.     

Spins and mixing ratios in 138Ba

The spin assignments to the 1899 (4⁺), 2308 (3⁺ or 4⁺) and 2446 (3⁺) keV levels in ¹³⁸Ba have been confirmed by γ-γ directional correlation measurements. In addition, the multipolarity and $\text{E2}\text{M1}$ mixing parameters for a number of transitions have been established as follows: 409 keV (M1+E2, ?0.75 < δ < ?0.45 or ?0.85 < δ < ?0.05 depending on the choice of J^π = 3⁺ or 4⁺ for the initial state), 463 keV (E2, 0 < δ < 0.15 for $\text{M3}\text{E2}$ admixture), 547 keV (M1+E2, ?0.06 < δ < ?0.015), 872 keV (M1+E2, δ undefined) and 1010 keV (M1+E2, ?0.015 < δ < +0.020).     

Nonadiabatic effects in the B, C, B′, and D states of H2

The Kolos-Wolniewicz potentials for the H₂$\text{B}{}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ and C¹Π_u states were used together with the hypothesis of pure precession for the rotation-electronic interaction, to calculate the nonadiabatic energy levels of these states for J = 1 to 5. The complete coupling matrix was computed using accurate numerical vibrational wavefunctions. The calculated Λ-doubling of the v = 0 to 12 C vibrational levels generally agrees well with experimental values, and the nonadiabatic shifts in the B rotational constants qualitatively explain the difference between the theoretical and RKR potentials for this state.The interaction of the B′${}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ and D¹Π_u states was also investigated, but only qualitatively since adiabatic potentials of sufficient accuracy do not exist for these states. The Λ-doubling of the Dv = 0 rotational levels agrees well with the experimental values. An appreciable “background” nonadiabatic shift in the B′ rotational constants was found. This shift, which is nearly 5 percent of B_v, is in addition to that of strong local two-level interactions and was not “deperturbed” in constructing the B′ RKR potential. The result is that the RKR turning points differ by about 0.04 au from the “true” adiabatic turning points. This conclusion is supported by a Hartree-Fock calculation of the B′ potential to the left of R_e.     

Oscillator strengths for the 2s2, 2p2, 2s3s(1S)-2s2p(1P) transitions of B(II)

Accurate configuration interaction wavefunctions for the 2s²(¹S), 2p²(¹S), 2s3s(¹S) and 2s2p (¹P) states of B(II) are calculated in a single optimized orbital basis of 7s, 6p and 4d Slater-type orbitals. 95, 84, 57 and 90% of the correlation energies, respectively, are realized by these wavefunctions. Oscillator strengths for the three ¹S-¹P transitions are calculated from these and from less accurate wavefunctions in the same orbital basis. The length values obtained from our most accurate wavefunctions, in order of increasing ¹S energy, are 0.9885, 0.202 and 0.007. The degree of accuracy of these oscillator strengths is estimated by noting the convergence to final values as increasing percentages of correlation energies are included in the wavefunctions together with the increasing agreement between length and velocity formulas. The exact theoretical oscillator strength for the resonant line is projected to be 0.985 with an error almost certainly not greater than ±0.015. The theoretical oscillator strengths for the other lines are considered to be 0.21±0.02 and less than 0.007, respectively.     

7Li + 54Fe Single-nucleon stripping reactions at E = 48 MeV

Angular distributions have been measured for the ⁵⁴Fe(⁷Li, ⁶Li/⁶He)⁵⁵Fe, ⁵⁵Co reactions at $\text{E(}{}^7\text{Li) = 48}\text{MeV}$. Exact finite-range DWBA calculations for both reactions, employing Woods-Saxon real and imaginary potentials to generate the distorted waves, reproduce the shape of the f-state angular distributions but not the rate of fall-off with increasing angle for p-states. Using real potentials constructed by double-folding a microscopic nucleon-nucleon potential with a Woods-Saxon shaped imaginary potential to generate the distorted waves did not change the calculations. The forward angle (⁷Li, ⁶He) data allowed the $\text{2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ states in ⁵⁵Co to be located and the determination of the single-particle centroid energies. The ⁵⁵Co spectroscopic factors are in good agreement with those from the (d, n) reaction but are generally 25 % lower than those from average (³He, d) results. The ⁵⁵Fe spectroscopic factors are in good agreement with (d, p) results.     

The eikonal approximation and E(2) invariance

A group theoretic interpretation is given for the eikonal approximation in potential scattering. This is based upon the approximate invariance at high energies under translations and rotations in the transverse scattering plane; that is, symmetry under the group E(2). The Lippman-Schwinger equation is formulated in a set of basis states which transform invariantly under irreducible representations of E(2) and the solution for the eikonal Hamiltonian, together with lowest order (Saxon-Schiff) corrections is obtained within this basis. A formulation of unitarity in the impact-parameter representation, based upon the E(2) invariance is given. The “geometrical” interpretation of this representation, in connection with the eikonal approximation, is made clear by our approach.     

VAMPIR calculations for 128Ba and 130Ce: Two mechanisms of backbending

Hartree-Fock-Bogoliubov calculations with spin and number projection before the variation (VAMPIR) are performed for the nuclei ¹²⁸Ba and ¹³⁰Ce using a slightly renormalized Brueckner G-matrix as effective interaction in a rather large single-particle basis. The results are compared to those of Hartree-Fock-Bogoliubov calculations with projection after the variation, those of multiconfiguration calculations (MONSTER) and to experiment. In both nuclei the VAMPIR and the MONSTER approaches turn out to be of about the same quality and agree rather well with the experimental data. Analysis of the VAMPIR mean fields reveals that two somewhat different mechanisms are responsible for the backbending observed in the yrast bands of the two nuclei. While in ¹³⁰Ce the well-known alignment of two high-j quasiparticles (proton $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$) is found, in ¹²⁸Ba first a neutron pair is scattered from the $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ to the $\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ orbit, and then the larger alignment energy of the less occupied neutron $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ states produces the backbend. This latter effect is in agreement with the predictions of a simple model presented by us some years ago.     

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.     

Elastic and inelastic scattering of 6Li and 7Li by 54Fe at E = 36–50 MeV

Detailed angular distributions for the elastic and inelastic scattering of ⁷Li at E = 36, 42, and 48 MeV and of ⁶Li at E = 38, 44, and 50 MeV by ⁵⁴Fe have been measured. It is not possible to describe both sets of data with the same set of optical-model parameters. The ratio of $\text{U}\text{W}$ is 0.8 for ⁷Li and 1.4 for ⁶Li at the strong absorption radius, implying stronger absorption for ⁷Li than for ⁶Li. No energy dependence in the optical-model parameters was necessary for either ⁶Li or ⁷Li. The inelastic scattering from the ⁵⁴Fe 2⁺, 1.41 MeV state was well described by the DWBA and the extracted deformation length (βR = 0.62) was the same for both ⁶Li and ⁷Li scattering. It was not possible to describe the ⁷Li projectile excitation data with collective-model DWBA calculations showing that more detailed calculations for the projectile excitation are necessary.     

The B(E2) for the first 2 state in Zr

A model-independent measurement of the width of the first 2⁺ state (2.186 MeV) of ⁹⁰Zr has been carried out using the resonant scattering of bremsstrahlung and its detection with a Ge(Li) detector. The observed resonance fluorescence yield corresponds to a reduced E2 transition probability B(E2↑) = 608 ± 35 e² · fm⁴. The difference between this value and recent inelastic electron scattering results exceeds the range usually attributed to the model dependence of the latter.     

Absolute band strengths for the AlO blue-green (B2σ−X2σ) band system

The relative intensity measurements of Linton and Nicholls¹ on the AlO blue-green system have been placed on an absolute scale using the radiative lifetimes of Johnson et al.² and Dagdigian et al.³ for levels of the B²Σ state of AlO. Absolute values of Einstein A coefficients, band strenghts and band oscillator strengths are presented for 75 bands of the system.     

The 6Li(α, 2α)2H reaction at 700 MeV and the α-d momentum distribution

The results of an experimental study of the reaction ⁶Li(α, 2α)²H at 700 MeV are given. A comparison with the data from seven other reactions pertaining to the α⁺d cluster structure of ⁶Li is presented. The amplitude for the virtual transition ⁶Li→α+d obtained three of these experiments and the present one are comparable. The internal momentum distributions extracted with the plane-wave impulse approximation in four of the experiments are compatible with a pole form, the width parameter being given by the α-separation energy in ⁶Li. The remarkable consistency among these results is seen as evidence for the validity of the simple models used for both the reaction mechanism (PWIA) and to describe the α d-vertex (pole approximation) in ⁶Li.     

Raman scattering spectra of B2-polariton and B2 (LO) modes in paraelectric KDP

The first observation of B₂-polariton and B₂ (LO) modes in the paraelectric phase of KDP has been made by the z(xy)z + Δy and z(xy)z? Raman scattering experiments, respectively. The B₂-polariton (θ = 0.20–0.48°) spectra has revealed both the Stokes and anti-Stokes peaks. The LO-mode which is nearly critically damped has been observed. From these results the lowest B₂ mode spectrum obtained by the y(xy)x Raman scattering has been reconfirmed to be oscillatory in nature, that is, a transverse optical phonon excitation.