Dipole bands in nucleus ~(139)pm

High-spin states in nucleus (~139)Pm have been studied using the reaction ~(116)Cd(~(27)Al, 4n)~(139)Pm. Two dipole cascades have been found. Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei (DCO) ratios and systematic behavior in neighboring odd-proton nuclei. The level structures of ~(139)pm are compared with those of the N = 78 isotone ~(141)Eu in which two dipole bands have been confirmed as magnetic rotational bands. The close similarity between them suggests that the dipole bands in ~(139)Pm may be magnetic rotational bands.     

139Pm核中磁转动带的研究

通过重离子熔合蒸发反应116Cd(27Al, 4n)布居了139Pm的高自旋激发态,用12台高纯锗探测器（HpGe）阵列进行了在束γ-γ 符合测量。 基于γ-γ符合关系及139Pm核已知的能级信息,建立了两条ΔI=1的负宇称带。 利用相邻核能级结构的系统性和依据半经典的核子-核子有效作用的理论模型（SPAC）对这两条带能级结构进行了定量计算, 认为它们属于磁转动带。 High spin states in 139Pm have been studied via the116Cd(27Al, 4n) heavy ion fusion evaporation reaction. The γ-γ coincidences were measured with 12 HpGe detectors. Based on γ-γ coincidence relationships and previously known levels in 139Pm, two ΔI＝1 negative parity bands have been established. From the systematic comparison with the neighbouring nuclei and semi classical effective interaction model (SPAC) calculations, the two bands were suggested as magnetic rotational bands.     

On-line nuclear orientation of the deformed neutron-deficient Eu,Sm and Pm isotopes

Low-temperature nuclear orientation measurements made on-line at the SERC Daresbury Laboratory on^142m Eu,^141m Sm, and¹⁴¹Pm, with known magnetic dipole moments, have yielded the magnitude of the hyperfine fields of these isotopes in an iron host lattice. Thus measurements for the isotopes^{139, 138}Eu,^139m Sm, and¹³⁸Pm yielded values for the respective magnetic moments. Limits on the thermal relaxation times of Eu and Sm isotopes in Fe were also deduced. The results for¹³⁸Eu appear to contradict the earlier πh_11/2⊗νh_11/2 ground-state configuration assignment.     

Systematic study of odd-mass 151-161Pm and 154,156Pm isotopes using projected shell model

Inspired by the availability of recent experimental as well as theoretical data on the energy levels of odd-mass ^151-161Pm and odd-odd ^154,156Pm, we applied the theoretical framework of the projected shell model to further understand the nuclear structure of these nuclei. The calculations closely reproduced the experimental data reported for the yrast bands of these isotopes by assuming an axial (prolate) deformation of ~0.3. Other properties along the yrast line, such as transition energies and transition probabilities, have also been discussed. Band diagrams are plotted to understand their intrinsic multi-quasiparticle structure, which turn out to be dominated by 1-quasiparticle bands for the odd-mass Pm isotopes and 2-quasiparticle bands for the doubly-odd Pm isotopes under study. The present study not only confirms the recently reported experimental/theoretical data, but also extends the already available information on the energy levels and adds new information regarding the reduced transition probabilities.     

High spin investigation in 193Pb with EUROGAM 2: coexistence of superdeformed and dipole bands

The nucleus ¹⁹³Pb was populated via the ¹⁶⁸Er(³⁰Si, 5n) reaction at a beam energy of 159 MeV and studied with the EUROGAM II spectrometer. Five new dipole ΔI = 1 cascades have been found. The ¹⁹³Pb dipole bands are discussed in terms of microscopic HF+BCS calculations. The proposed configurations are based on a high-K two-quasiproton excitation coupled to rotation aligned quasineutrons. Parallel to the dipole bands the six superdeformed bands have been discussed in the framework of microscopic mean-field calculations. The bands are interpreted as three pairs of signature partners based on quasineutron excitations. Cross-talk transitions linking two signature partner superdeformed bands have been observed and, for the first time in lead isotopes, a mean B(M1)/B(E2) ratio value of 0.15±0.04 μ _N ² /e^2b2 has been extracted.     

The magnetic dipole moment of the 91 keV state of147Pm

The magnetic dipole interaction of the 91 keV state of¹⁴⁷Pm in an environment of metallic neodymium has been investigated by a time-differential perturbed angular correlation (TDPAC) experiment. The measurement was performed in an external magnetic field of 2.94 (3) T at room temperature. From the Larmor precession frequency the magnetic dipole moment of the 91 keV state is derived as =+3.22(16) _K. The enhancement of the external magnetic field by the paramagnetic 4f shell determines the ionicity of the Pm ion as Pm³⁺ in metallic and as Pm⁴⁺ in non-metallic sources.     

Investigation of lifetimes in the dipole band of 139Sm

Lifetimes have been measured for a dipole band in ¹³⁹Sm using DSAM. The deduced B(M1) and B(E2) values as well as B(M1)/B(E2) ratios are compared with calculations in the framework of the TAC (Tilted Axis Cranking) and SPAC (Shears mechanism with Principal Axis Cranking) models. The dipole band in ¹³⁹Sm can be considered as a magnetic rotational band with a prolate or triaxial nuclear deformation.     

Isotope shifts in spectra of molecular liquids

In the IR absorption spectra of low-temperature molecular liquids, we have observed anomalously large isotope shifts of frequencies of vibrational bands that are strong in the dipole absorption. The same effect has also been observed in their Raman spectra. At the same time, in the spectra of cryosolutions, the isotope shifts of the same bands coincide with a high accuracy (±(0.1–0.5) cm^–1) with the shifts that are observed in the spectra of the gas phase. The difference between the spectra of examined low-temperature systems is caused by the occurrence of resonant dipole–dipole interactions between spectrally active identical molecules. The calculation of the band contour in the spectrum of liquid freon that we have performed in this work taking into account the resonant interaction between states of simultaneous transitions in isotopically substituted molecules can explain this effect.     

Sensitive detection of flame absorption spectra of rare-earth elements with a dye laser

The dye-laser amplified absorption method is applied to observe the atomic absorption lines of rare-earth elements in a nitrous-oxide-acetylene flame. All of the rare-earth elements except Pm are analyzed and about 1200 lines have been recorded within the continuous spectral region from 432 to 670 nm. A much larger number of absorption lines can be detected than those measured by the traditional method. The absorption bands of monoxide molecules have also been detected.     

Investigation of lifetimes in dipole bands of 142Gd

Lifetimes have been measured for dipole bands in ¹⁴²Gd using DSAM. The deduced B(M1) and B(E2) values as well as B(M1)/B(E2) ratios are compared with calculations in the framework of the TAC (Tilted Axis Cranking) and SPAC (Shears mechanism with Principal Axis Cranking) models. The dipole bands DB1 to DB4 can be interpreted as magnetic rotational bands.     

Nuclear spins and moments: Fundamental structural information

Predictions for the low energy structure of well deformed odd-A Pm and Sm nuclei in the A ≈ 130 region are given, based on the particle-rotor model. Distinctive magnetic dipole properties (static moments and transition rates) are expected for certain Nilsson configurations, and comparisons to recent data are made for¹³³Pm,¹³⁵Sm and¹³³Sm.     

Shears bands in 112In

A new level scheme of 112In have been established up to 6.8 MeV in excitation energy and to a tentative spin of (21+) through the reaction 110Pd(7Li,5n)112In at a beam energy of 50 MeV. In-beam measurements involving γ-γ coincidences and directional correlation of oriented states were performed. M1 bands consisting of/△I = 1 dipole transitions have been observed. Possible quasiparticle configurations suggest that these bands are similar to the shears bands observed in Pb nuclei.     

Kernspektroskopische Untersuchungen zu den Termschemata einiger Nuklide im Bereich der abgeschlossenen NeutronenschaleN=82:141Pr,143Pm,139Pr und141Pm

The level schemes of the nuclei¹⁴¹Pr,¹⁴³Pm,¹³⁹Pr, and¹⁴¹Pm were investigated by measuring theγ-spectra following theΒ-(decay of the corresponding (Z+1)-isobars. The existing level schemes for these nuclides were thereby enlarged or revised. The results are discussed using the weak-coupling picture.     

Risk of misinterpretation of nearly degenerate pair bands as chiral partners in nuclei

The experimental information on the observed nearly degenerate bands in the N = 75 isotones, in particular 134Pr and 136Pm, which are often considered as the best candidates for chiral bands, is critically analyzed. Most properties of the bands, in particular, the recently measured branching ratios and lifetimes, are in clear disagreement with the interpretation of the two bands as chiral bands. For I =14-18 in 134Pr, where the observed energies are almost degenerate, we have obtained a value of 2.0(4) for the ratio of the transition quadrupole moments of the two bands, which implies a considerable difference in the nuclear shape associated with the two bands. The insufficiency of the near-degeneracy criterion to trace nuclear chirality is emphasized.     

Evidence for second-phonon nuclear wobbling

The nucleus 163Lu has been populated through the reaction 139La(29Si,5n) with a beam energy of 157 MeV. Three triaxial, strongly deformed (TSD) bands have been observed with very similar rotational properties. The first excited TSD band has earlier been assigned as a one-phonon wobbling excitation built on the lowest-lying (yrast) TSD band. The large B(E2)(out)/B(E2)(in) value obtainable for one of four observed transitions between the second and first excited TSD bands is in good agreement with particle-rotor calculations for a two-phonon wobbling excitation.     

M1 and E2 band structures in the Sn-Xe-Ba region

In the present talk I will discuss some ‘rare’ aspects of the E2 band structures and the novel features concerning the dipole bands in this mass region. Reliable and accurate lifetimes have been measured using coincidence recoil distance method. The results of ^129,130Ba will be discussed. In contrast to the predictions of the tilted axis cranking model, the dipole bands in Sb-Xe-Ba nuclei can be nicely described as high-K prolate bands. New data from multi-detector arrays has established extended bands structure, their decay to low lying states have been established and the angular correlation supports the predominant, ΔI=1 character. Finally the sensitive measures, i.e. B(M1) rates of the tilted axis model are compared with the high-K formula based on 1-dim cranking model.     

Nuclear electromagnetic moments of the ground states of148Pm and210Bi calculated with phenomenological wave functions derived from analyses ofβ-decay experiments

Zeitschrift für Physik A Hadrons and nuclei - The magnetic dipole and electric quadrupole moments of the ground states of148Pm and210Bi are evaluated with phenomenological wave functions...     

Development of magnetic rotation in light Gd nuclei; study of 142Gd

High-spin states in ¹⁴²Gd have been populated by means of the ⁹⁹Ru(⁴⁸Ti, 2p3n) reaction at 240 MeV and investigated with the γ-spectrometer EUROBALL III and the charged-particle detector array ISIS. The features of four dipole bands have been determined and compared with tilted-axis cranking model calculations indicating that they are magnetic rotational bands. A transition from regular to irregular bands has been found approaching N = 82 demonstrating that this is a general phenomenon in nuclei near a double-shell closure. Received: 9 December 2001 / Accepted: 9 January 2002     

A theoretical study of the effect of disorder of the transition dipole moments of molecules on the shape of optical bands of molecular aggregates

Aggregates with substitutional disorder, in which molecules of different types have different transition dipole moments, are considered. The relations between the absorption spectra of aggregates with disordered and nondisordered transition dipole moments are obtained for two limiting cases: (1) the case when there is no statistical correlation between the transition energies and transition dipole moments of the molecules and (2) the case of total correlation, when the transition energies and transition dipole moments are strictly related to each other. For aggregates that are characterized by substitutional disorder along with diagonal disorder, an effective method of calculation of the optical bands is developed. Numerical calculations of the absorption bands of aggregates consisting of molecules of two types are carried out at different values of the parameters.     

LaⅡ5d2 1G4→4f5d 1F3超精 细结构光谱测量

利用少有的共线快离子激光光谱学方法研究了LaⅡ的超精细结构,测量了5d² < sup>1G₄态→4f5d ¹F₃态的超精细结构光谱,分 别得出了相应的磁偶极矩和电四极矩的超精细相互作用常数. 关键词： 共线快离子束激光光谱学 超精细结构 共振激发