Nuclear levels in228Th populated in the decay of228Pa

The electron-capture decay of²²⁸Pa to levels in²²⁸Th has been studied using mass-separated sources and high-resolutionγ-ray and conversion-electron spectroscopy. A level at 979.5 keV is assigned as 2⁺ member of a second excited K_π=0⁺ band, with the 0⁺ band head at 938.6 keV. The 2⁺ and 3⁺ members of a second excited K_π=2⁺ band at 1153.5 and 1200.5 keV, which decay by strongE0 transitions to the 969 keVγ-vibrational band, are confirmed. In addition we tentatively propose a K_π=1⁺ band at 944 keV. The K_π=0^?, 1^? and 2^? members of the octupole quadruplet are confirmed, and theγ decay of these levels is analysed in an approach, in which the mixing of the octupole bands by the Coriolis interaction is taken into account. It is suggested that octupole correlations might be important for theE1 transition moments. A total of 29 levels is observed between ～1.4 and ～2.0 MeV, for which the nuclear structure, and the possible assignment to rotational bands, is unclear.     

Coulomb excitation of230Th with32S,84Kr and142Nd projectiles

The Coulomb excitation measurements for the²³⁰Th nucleus with³²S,⁸⁴Kr and¹⁴²Nd projectiles are presented. The use of different projectiles allowed us to get information in the ground-state band and side bands. The energy spectrum of the ground-state band and of the lowest negative-parity band have been investigated up to the spin valueI=24⁺ andI=19^?(21), respectively. Five side bands (K ^π=0⁺, 2 ₁ ⁺ , 2 ₂ ⁺ , 1^?, 2^?) were observed also. The branching ratios for a large number of transitions in the spin regionI≦10 for π=+1 andI≦9 for π=? 1 are analysed. The full set of experimental data contains information on the mixing of the adiabatic states and on the nuclear response to the electromagnetic field ofγ-radiation. It is shown that the experimental data may be explained taking into account the coupling of the ground-β- and twoγ-bands and also of theK ^π=0^?, 1^? and 2^? negative-parity bands. An enhancement of the transitions from theγ-to theβ-band in respect to the transitions from theγ to the ground band and from theβ- to the ground band is reported. The mixing of the negative-parity bands is found to be typical for the alignment of the octupole-vibrational angular momentum. The strong spin dependence of the intrinsic matrix elements of the electric-dipole operator follows from the branching ratios of inter- and intra-band transitions from theK ^π=0^? states.     

The (p,t) reactions on nuclei in the rare earth region

The (p, t) reactions on isotopic targets of ^{178, 180}Hf and all the stable isotopes of Yb and on natural targets of Gd, Dy, Er, Hf, Ta, W, Os and Au were studied at a beam energy of 19 MeV with an average resolution of 12 keV. A split-pole magnetic spectrometer was used to measure (p, t) Q-values and absolute differential cross sections. On the basis of angular distribution shapes definite 0⁺ and tentative 2⁺ assignments were made. Rotational bands were identified assuming an I(I+1) spacing. The (p, t) reaction populates excited 0⁺ states strongly in ¹⁷⁴Yb, ¹⁷⁶Hf, ¹⁶⁶Yb and several Gd, Dy and Er isotopes. The ¹⁷⁴Yb and ¹⁷⁶Hf 0⁺ states are discussed in terms of the pairing phase transition and in terms of Nilsson orbitals with unequal (p, t) reaction amplitudes. Members of gamma and octupole vibrational bands were observed in the even-N nuclei. The lowest L = 0 transfers to states in ^{169, 171}Yb were found to have less than 55% of the strength to ground states in adjacent even-N nuclei. A strong L = 0 transfer to a state at 1513 keV in ¹⁷¹Yb indicates the presence of a possible K = 0 core vibration coupled to the unpaired $\text{5}\text{2}$[512] neutron. The natural targets have furnished information on trends in cross sections for members of ground bands, gamma bandheads, 3^? octupole states, and strongly excited 0⁺ states.     

<Emphasis Type="Italic">J</Emphasis><Superscript>π</Superscript>0<Superscript>−</Superscript> levels in <Superscript>156</Superscript>Gd and <Superscript>158</Superscript>Gd

The 0^? states in the ¹⁵⁶Gd nucleus at E = 1952.38 keV and in the ¹⁵⁸Gd nucleus at E = 2269.16 keV are established on the basis of an analysis of available data on even-even deformed nuclei. From data on the deexcitation of the levels and on the probability of their population by beta transitions, it is found that these states have a two-particle proton structure. A comparison of our data with information about the 0^? levels in the ¹⁷⁰Yb and ¹⁷⁶Hf nuclei makes it possible to conclude that J^π0^? two-particle states exist at an excitation energy of about 2 MeV and higher.     

Band interaction in <Superscript>162</Superscript>Dy, <Superscript>168</Superscript>Er,and <Superscript>172</Superscript>Yb

Coriolis interaction between levels of two rotational bands in ¹⁷²Yb with K ^π = 2⁺ and 3⁺ and in ¹⁶⁸Er between levels with K ^π = 0^?, 1^?, and 2^? is studied. The values of the interaction parameters are obtained. The mutual influence of two bands in ¹⁶²Dy with ΔK = 2, K _i ^π = 0 ₂ ⁺ and 2 ₁ ⁺ due to Coriolis interaction is demonstrated.     

Levels in 156Gd studied in the (n, γ) reaction

Levels up to 2.3 MeV in ¹⁵⁶Gd have been studied using the (n, γ) reaction. Energies and intensities of low-energy γ-rays and electrons emitted after thermal neutron capture have been measured with a curved-crystal spectrometer, Ge(Li) detectors and a magnetic electron spectrometer. High-energy (primary) γ-rays and electrons have been measured with Ge(Li) detectors and a magnetic spectrometer. The high-energy γ-ray spectrum has also been measured in thermal neutron capture in 2 keV resonance neutron capture. The neutron separation energy in ¹⁵⁶Gd was measured as S_n = 8535.8 ± 0.5 keV.About 600 transitions were observed of which ~50% could be placed in a level scheme containing more than 50 levels up to 2.3 MeV excitation energy. 42 of these levels were grouped into 15 excited bands. In addition to the β-band at 1050 keV we observe 0⁺ bands at 1168, 1715 and 1851 keV. Other positive-parity bands are: 1⁺ bands at 1966, 2027 and 2187 keV; 2⁺ bands at 1154 (γ-band) and 1828 keV; and 4⁺ bands at 1511 and 1861 keV. Negative-parity bands are observed at 1243 keV (1^?), 1366 keV (0^?), 1780 keV (2^?) and 2045 keV (4^?). Reduced E2 and E0 transition probabilities have been derived for many transitions. The ground band, the β- and γ-bands and the 0⁺ band at 1168 keV have been included in a phenomenological four-band mixing calculation, which reproduces well the experimental energies and E2 transition probabilities.The lowest three negative-parity (octupole) bands of which the 0^? and the 1^? bands are very strongly mixed, were included in a Coriolis-coupling analysis, which reproduces well the observed energies. The E1 transition probabilities to the ground band are also well reproduced, while those from the higher-lying 0⁺ bands to the octupole bands are not reproduced. Absolute and relative transition probabilities have been compared with predictions of the IBA model and the pairingplus-quadrupole model. Both models reproduce well the E2 transitions from the γ-band, while strong disagreements are found for the E2 transitions from the β-band. The IBA model predicts part of the decay features of the higher lying 2⁺₂, 4⁺₁ and 2^?₁ bands.     

High-spin spectroscopy of168Hf

The nucleus¹⁶⁸Hf was studied up to spin (38⁺) in the yrast band and to spins (41^?) and (38^?) in the lowest two negative-parity bands. The onset of a proton alignment (h_9/2 or i_13/2 quasiparticles) is observed in these three bands for the highest transitions. A new band with even spins and negative parity was found. The interaction strength between the ground-state band and theAB band is measured.     

Levels of 234U and 236U excited by the (d,d') reaction

The energy levels of ²³⁴U and ²³⁶U have been studied through the inelastic scattering of 16 MeV douterons. A magnetic spectrograph was used to momentum-analyse the scattered deuterons at θ = 90° and 125°. Excited in both ²³⁴U and ²³⁶U were the ground state bands up to and including the 8⁺ members, the K^π = 0⁺β-vibrations, the K^π = 2⁺γ-vibrations, and the K^π = 0^? octupole vibrational bands. In ²³⁴U, additional levels at 1023 and 1126 keV are ascribed to a K^π = 2^? band, levels at 1238, 1312, and 1446 keV are identified as members of either a K^π = 0^? or 1^? configuration, and other tentative assignments are made for members of K^π = 1^? and 3^? configurations. Relative reduced transition probabilities, B(E2), to the 2⁺ rotational and γ-vibrational states are generally found to be in good agreement with Coulomb excitation measurements. Relative B(E3) values for the 3^? states excited are slightly higher than the predictions of a microscopic theory of octupole vibrations.     

Gamma deexcitation of the 180m Ta isomer

Vibrational states built on the K ^π = 9^? isomer and on the ground state (K ^π = 1⁺) in ¹⁸⁰Ta are calculated within the quasiparticle-phonon nuclear model using the ¹⁷⁸Hf nucleus as a core. A procedure for calculating the rates of K-allowed γ-ray transitions from vibrational states built on the isomer to those built on the ground state is presented. The probabilities of two-step processes consisting of a dipole excitation of the isomer and successive E1 and E2 transitions from them to vibrational states built on the ground state of the ¹⁸⁰Ta nucleus are calculated. Two-step transitions from the isomer to vibrational states below 2.7 MeV and to the vibrational states built on the ground state appear to be very weak. There are many E1 transitions from the vibrational states built on the isomer to the vibrational states built on the ground state. They are weak and cannot be responsible for the strong deexcitation of ^180m Ta in the relevant (γ, γ′) reaction. A decisive role is played by collective E2 transitions from dipole excitations in several excitation energy intervals ranging between 2.7 and 4.0 MeV. These highly intense K-allowed two-step γ-ray transitions can be responsible for the strong deexcitation of the ^180m Ta state in the (γ, γ′) reactions.     

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.     

Excited levels of 148Ce

Available experimental data on excited levels of the ¹⁴⁸Ce nucleus are analyzed. With the aid of model concepts and systematics that cover neighboring nuclei, the spectrum of ¹⁴⁸Ce is supplemented with a K ^π = 2^? rotational band that has a bandhead at 1368.98 keV, which extends up to the 16^? state at 3897.9 keV, and which is new. Three states at E = 1422.85, 1786.57, and 2198.6 keV of spin-parity 5⁺, 7⁺, and 9⁺, respectively, are included in the gamma-vibrational band featuring the known 2⁺ and 3⁺ levels at 989.90 and 1116.63 keV, respectively. A significant difference in the behavior of the moments of inertia in positive-and negative-parity bands is highlighted.     

Gammaübergänge und Energieniveaus in Dy 165

220 neutron capture Gamma rays of Dy 165 were measured with the Risø curved crystal spectrometer. The intense transitions permitted the construction of a level scheme for this oddN nucleus. The rotational bandsK=7/2⁺[633],K=1/2^?[521] andK=5/2^?[512] were precisely localized, including the spin 11/2 states. Gammavibrational bands built on these Nilsson orbits were observed with their band heads at 538.6, 573.5 and 570.2 keV. TheI=5/2 term at 533 keV can be considered as the 5/2^?[523] Nilsson state. The branching ratios allowed the determination of (g _K?g^R)²-factors for the [633], [521] and [512] bands and yieldedE 1-hindrance factors.     

The decay of174Ta

Levels in¹⁷⁴Hf excited in the decay of¹⁷⁴Ta have been studied. Measurements of gamma-rays, conversion electrons and gamma-gamma-time coincidences were performed. The ground state band, the beta-vibrational band, the gamma-vibrational band with its head at 1226.81 keV, aK=3⁺ band at 1303.42 keV and aK=2^? octupole band at 1308.67 keV were observed. Several 2⁺ levels withK=0 are excited. The mainβ ⁺-branches proceed through allowed or first-forbidden transitions to the 2⁺ and 4⁺ levels of the ground state band. The character of theI ^π=3⁽⁺⁾ ground state of¹⁷⁴Ta is discussed.     

On the <Emphasis Type="Italic">K</Emphasis><Superscript><Emphasis Type="Italic">π</Emphasis></Superscript> = 0<Superscript>+</Superscript> rotational bands in the <Superscript>178</Superscript>Hf nucleus

The results obtained by studying the angular distributions of gamma rays with respect to the neutron-beam axis in the reaction ¹⁷⁸Hf(n, n′γ) involving the deexcitation of the K ^π = 0⁺ rotational bands of ¹⁷⁸Hf are presented.New information about themultipole-mixing parameter δ in gamma transitions from the levels of these bands is obtained. The K ^π = 0₄⁺ band is constructed anew. The relationship between the parameter δ for the (2⁺0 _n −2⁺0₁) gamma transition and the energy gap Δ _n = E _lev(2⁺0 _n ) − E _lev(0⁺0 _n ), on one hand, and the quasiparticle structure of the rotational band, on the other hand, is discussed for ¹⁷⁸Hf on the basis of the quasiparticle-phonon model.     

Structure of levels of the 160Gd nucleus

The scheme of excited levels of the ¹⁶⁰Gd nucleus was refined and extended owing to the addition of the K _?? = 2^? band and the inclusion of new rotational states in other bands. Data for the respective (n, n???) reaction from the literature were used. The signature splitting of K = 1 bands was found.     

Electric properties of levels of 156Dy rotational bands

The nonadiabaticity of E0 transitions from 0 ₂ ⁺ states and 2 ₁ ⁺ bands in ¹⁵⁶Dy is examined within a phenomenological model that takes into account the mixing of K ^π = 0 ₁ ⁺ , 0 ₂ ⁺ , 0 ₃ ⁺ , 2 ₁ ⁺ states and 1⁺-bands. It is shown that the nonadiabaticity of E0 transitions is due primarily to the mixing of 0 ₂ ⁺ and 0 ₃ ⁺ bands.     

Analysis of the CRDS spectrum of 18O3 between 6950 and 7125 cm−1

The absorption spectrum of the ¹⁸O₃ isotopologue of ozone was recorded by CW-Cavity Ring Down Spectroscopy in the 6950–7125 cm^?1 region. The typical noise equivalent absorption of the recordings is α_min ≈1×10^?10 cm^?1. The spectrum is dominated by three very weak bands: 3ν₁+5ν₃ near 7009 cm^?1 and the ν₂+7ν₃ and 4ν₂+5ν₃ interacting bands near 7100 cm^?1. In total 260, 206 and 133 transitions were assigned for the 3ν₁+5ν₃, ν₂+7ν₃ and 4ν₂+5ν₃ bands, respectively. The line positions of the 3ν₁+5ν₃ band were modelled using an effective Hamiltonian (EH) model involving two dark states – (6 0 1) and (2 5 2) – in interaction with the (3 0 5) bright state. The EH model developed for the ν₂+7ν₃ and 4ν₂+5ν₃ bands involves only the (0 1 7) and (0 4 5) interacting bright states. Line positions could be reproduced with rms deviations on the order of 0.01 cm^?1 and the dipole transition moment parameters were determined for the three observed bands. The obtained set of parameters and the experimentally determined energy levels were used to generate a list of 984 transitions of the three bands which is provided as Supplementary Material.     

Neutroneneinfangs-Gammaspektrum und Niveauschema von Erbium 167

The (n, γ)-spectrum of Er 167 was investigated by means of the Risø bent crystal spectrometer. The energies and intensities of 47 transitions were measured. 22 of them were fitted into a level scheme. The rotational bands of theK=7/2⁺[633],K=1/2^?[521], andK=5/2^?[512] states were found up to the spin valuesI=11/2⁺, 9/2^?, and 7/2^?. Gammavibrational states of these Nilsson orbitals were determined or proposed. The energy of theK=5/2^?[523] state was suggested. Branching ratios of gamma transitions were compared with theoretical predictions.     

Correlation femtoscopy of Kaons in the SELEX experiment

Preliminary results from the correlation femtoscopy of identical kaons in the SELEX experiment (Fermilab E781) are presented. Kaons are selected in inclusive reactions of Σ^?C(Cu) interactions at an initial energy of 610 GeV. Kaon pairs are studied in all possible charged states: K _s ⁰ K _s ⁰ , K _s ⁰ K⁺, K _s ⁰ K^?, K⁺K⁺, K⁺K^? and K^?K^?. The source sizes of the hadronization region of neutral and charged kaon pairs are measured.