Signature splitting in magnetic rotational bands

Nearly-spherical nuclei in three mass regions have recently been observed to exhibit rotational-like features. We have identified almost 80 such bands; largest number (43) lie in the lead region. Most of these bands are assigned oblate multi-quasiparticle configurations. Their interpretation in terms of ‘magnetic rotation’ does not allow for signature splitting in these bands. We have however found signature splitting as well as signature inversion in many bands. We apply the two-quasiparticle plus rotor model to understand the occurrence of signature splitting vis-a-vis the role of ‘shears mechanism’ in these bands.     

A=100区奇奇核旋称反转

利用两准粒子加轴对称转子模型,对A=100质量区两个奇奇核¹⁰²Rh和^{9 8}Rh的旋称反转进行了研究.结果表明,在A=160,130,80三个质量区奇奇核的计算中 已得到证实的、可能的旋称反转机制(即低K空间n-p相互作用和科氏力的相互竞争),对 于A=100质量区奇奇核也是适用的.这暗示在不同质量区奇奇核可能存在一种普遍的旋称 反转机制. 关键词： 奇奇核 旋称反转 两准粒子加轴对称转子模型     

The odd-even shifts in odd-odd deformed nuclei based on residual interaction studies

Residual interaction calculations have been made for predicting the sign and the magnitude of the odd-even shifts observed in the rotational levels of theK=0 bands in the doubly-odd rare earth nuclei. It is shown that, contrary to the conclusions reached in earlier studies, the same zero-range spin-dependent residual interaction can reproduce the odd-even shifts as well as the GM splitting energies. This has been made possible with the inclusion of the phase factors for the total intrinsic spin and the total parity of the two-quasi-particle states in the Newby matrix elements. Predictions are made for the odd-even shifts for otherK=0 bands arising from several configurations not confirmed or observed so far.     

Transverse superresolution and focal shift with rotational tunable phase mask

This paper reports the imaging characteristics of an optical system can be modified by our designed polarization pupil mask. The novel rotational symmetric polarization pupil mask design based on combination of half-wave and quarter-wave plates is introduced for realizing the focal shift and extending focal depth of an optical system and the procedure for designing is presented. Numerical results show when an appropriate rotational symmetric polarization pupil mask is used as an apodizer in the optical imaging system, it not only can effectively achieve the continuously focal shift in a small range and extend focal depth of the optimized system, but also can evidently increase the transverse resolution of the optimized system at the genuine focal plane.     

High-resolution measurements of pressure self-broadening and shift for the metyl-cyanide rotational J=1−0 line

Summary The capabilities of the travelling-wave spectrometry in the field of high-resolution measurements of low-pressure gases at microwave frequencies are discussed. Some details about the main aspects of the experimental procedure and the data management, useful for the improvement of overall performances, are specified. A pressure broadening of (72.5±1.5) MHz/Torr and a pressure shift of (4.3±0.3) MHz/Torr are measured for theJ=1−0 rotational line of CH₃C¹⁴N. These results are more accurate than those previously reported and in better agreement with the theoretical predictions.

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Riassunto Si discutono le prestazioni di uno spettrometro a microonde ad onda progressiva nel campo della spettroscopia ad alta risoluzione in gas a bassa pressione. Sono in particolare considerati alcuni aspetti delle procedure sperimentali e dell'elaborazionedei dati che hanno portato a decisi miglioramenti nella sensibilità e nelle prestazioni complessive dell'apparato sperimentale. Sono stati misurati per la riga rotazionaleJ=1–0 di CH₃C¹⁴N un coefficiente di autoallargamento per pressione di (72.5±1.5) MHz/Torr e uno shift di (4.3±0.3) MHz/Torr. Queste misure risultano piú accurate di quelle precedentemente riportate e in migliore accordo con le previsioni teoriche.

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Резюме Обсуждаются возможности использования микроволнового спектрометра со скользящей волной для измерений с высоким разрешением в газах при низких давлениях. Рассматриваются основные аспекты экспериментальной процедуры и обработки данных, которые позволяют улучшить чувствительность аппаратуры. Измерены величины самоуширения с давлением (72.5±1.5) МГц/Тор и сдвига с давлением (4.3±0.3) МГц/Тор для ротационной линииJ=1–0 для CH₃C¹⁴N. Полученные результаты являются более точными, чем ранее опубликованные, и лучше согласуются с теоретическими предесказаниями.

     

Appearance of extrema in the frequency shift produced by scattering from a rotational anisotropic particle

We investigate the analytical expression of the spectrum that is produced by scattering of a polychromatic plane light wave incident upon a rotational anisotropic particle. It is found that the appearance of extrema in the frequency shift of the scattered field can be exactly predicted by our derived equations of the rotation angle. Numerical examples are presented to illustrate the theoretical results and also to show the impact of the effective radius of the scattering potential on the frequency shift.     

New rotational bands in 174Ta

Three new bands in ¹⁷⁴Ta have been identified by using the ¹⁶⁰Gd(¹⁹F,5n) reaction at beam energies of 87 MeV and 96 MeV. Nilsson configurations are assigned to these bands. In the 9/2⁻[514]_p+5/2⁻[512]_n band, the AB neutron crossing occurs at a rotational frequency of 0.30 MeV. This is indicative of the disappearance of the evidence for a reduction in neutron pair correlations. Received: 30 March 1998     

Air-broadened halfwidth and pressure shift coefficients of CO2 bands: 4750-7000 cm

Previously we obtained self-broadened halfwidth and self-induced shift coefficients at room temperature for 15 near infrared CO₂ bands between 4750 and 7000 cm⁻¹ [R.A. Toth, L.R. Brown, C.E. Miller, V.M. Devi, D.C. Benner, J. Mol. Spectrosc., 239 (2006) 243-271]. The present study expands our work on the near infrared line parameters of CO₂ to include air broadening coefficients. Here we report nearly 400 air-broadened half width and air-induced pressure shift coefficients spanning 11 different CO₂ vibrational bands in the 4750-7000 cm⁻¹ region. Retrievals have been performed using Voigt line profiles over three distinct spectral intervals: (a) 4750-5200 cm⁻¹, covering the 20011 ← 00001, 20012 ← 00001, and 20013 ← 00001 Fermi Triad and three associated hot bands 21111 ← 01101, 21112 ← 01101, 21113 ← 01101; (b) 6100-7000 cm⁻¹, covering the 30011 ← 00001, 30012 ← 00001, 30013 ← 00001 and 30014 ← 00001 Fermi Tetrad; (c) near 6950 cm⁻¹ for the 00031 ← 00001 overtone band. The air-broadened halfwidth and air-induced pressure shift coefficients have been modeled with empirical expressions and compared to other measurements available in the literature.     

Preliminary Lattice Study of I=0 KK Scattering

We deliver the realistic ab initio lattice investigations of KK^- scattering. In the Asqtad-improved staggered dynamical fermion formulation, we carefully measure KK^- four-point function in the I=0 channel by moving wall sources without gauge fixing, and clearly find an attractive interaction in this channel, which is in agreement with the theoretical predictions. An essential ingredient in our lattice calculation is to properly treat the disconnected diagram. Moreover, we explain the difficulties of these lattice calculations, and discuss the way to improve the statistics. Our lattice investigations are carried out with the MILC 2 ＋ 1 gauge configuration at lattice spacing a ≈ 0.15 fro.     

Effective decoupling in some odd-A odd-Z rotational bands

A systematic analysis of the results of single quasiparticle-plus-rotor bandmixing calculations is presented wherein the empirically noticed characteristic effective decoupling patterns and their systematics in certain odd-A odd-Z rotational bands based onh9/2, d1/2, h _11/2 andg _7/2 orbitals are reproduced. The strategy adopted allows us to obtain an almost unique set of parameter values for a given decoupling pattern. The composition of wavefunctions in terms of core rotational angular momentum supports the idea of effective decoupling. These wavefunctions are then used to analyse the extent and nature of Coriolis coupling in these bands. It is found that either one or both parts of the Coriolis energies, diagonal and non-diagonal, are significant in most of the cases and the non-diagonal part is mainly responsible for the effective decoupling. These Coriolis effects prominently affect the intrabandB(M1) andB(E2) values and their variation with spin is discussed. An unusual feature in theB(M1) value of theh9/2 orbital based band is pointed out.     

T = 0 versusT = 1 pairing in 0(36) limit of IBM-4 for heavyN = Z nuclei

In theO(36) limit of the interacting boson model including spin-isospin degrees of freedom (IBM-4), starting with a group chain that preservess andd boson spins and isospins together with a simple mixing hamiltonian, it is shown that the model generates, for heavyN =Z nuclei, even-even to odd-odd staggering in the number ofT = 0 pairs in the ground states for moderate difference in the basicT = 0 andT = 1s-boson pair energies; the staggering disappears when the energy difference is large.     

In-beam spectroscopy of thek π=0− bands in230–236U

TheK ^π=0^? bands in even uranium nuclei were studied in the compound reactions²³¹Pa(p, 2n)²³⁰U,^{230, 232}Th(α,2n)^{232, 234}U and²³⁶U(d, pn)²³⁶U. In-beamγ-rays were measured in coincidence with conversion-electrons, which were detected with an iron-free orange spectrometer. The negative-parity levels are observed up to intermediate spins (I<13^?). In addition, the 1^? and 3^? levels in²³⁰U were confirmed by a decay study with an isotope separated²³⁰Pa source. For the heavier isotopes (A≥232) the properties of theK ^π=0^? bands (energies andγ-branchings) are consistent with a vibrational character of these bands. For²³⁰U theK ^π=0^? band lies at rather low energy (E(1^?)=367 keV), and the level spacings within this band are very similar to those of the isotones²²⁸Th and²²⁶Ra, which might indicate the onset of a stable octupole deformation.     

The rotational spectrum and molecular parameters of ClO in the v=0 and v=1 states

The $\text{J =}\text{9}\text{2}\text{←}\text{7}\text{2}$, ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, ground vibrational state transitions of ³⁵ClO and ³⁷ClO and the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, excited vibrational state transitions of ³⁵ClO have been observed in the 164–167 GHz region. Additional measurements have also been made on the $\text{J =}\text{3}\text{2}\text{←}\text{1}\text{2}$ and $\text{J =}\text{5}\text{2}\text{←}\text{3}\text{2}$ transitions of both the ground and excited vibrational states. All measurements were made using millimeter oscillators which were phase locked to harmonics of a Hewlett-Packard microwave spectrometer's X-band source. Λ-doubling splitting of a few ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ transitions was resolved.When magnetic and nuclear quadrupole hyperfine terms off-diagonal in J and $\text{Ω}$ in the Hund's case (a) representation were included in addition to the usual diagonal terms, an excellent fit to all of our observed transitions resulted. The most significant change from previously determined parameters is the centrifugal distortion constant D for which the values, D₀ = 0.03972(26) MHz for ³⁵ClO, D₀ = 0.03888(32) MHz for ³⁷ClO and D₁ = 0.0395(21) MHz for ³⁵ClO are obtained. Values of 1.56959(1) Å for the equilibrium bond length and 854(7) cm^?1 for the equilibrium vibrational frequency are derived from the measured spectra. In addition, values for the Λ-doubling constant β_p and the quadrupole coupling constant eQq₂ were derived from the measured spectra for the first time.     

Dipole bands in nucleus ^139Pm

High-spin states in nucleus ^139Pm have been studied using the reaction ^116Cd（^27Al, 4n）^139Pm. 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 ^139Pm are compared with those of the N = 78 isotone ^141Eu in which two dipole bands have been confirmed as magnetic rotational bands. The close similarity between them suggests that the dipole bands in ^139Pm may be magnetic rotational bands.     

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.     

Coulomb energy differences in t = 1 mirror rotational bands in (50)Fe and (50)Cr

Gamma rays from the N = Z-2 nucleus (50)Fe have been observed, establishing the rotational ground state band up to the state J(pi) = 11+ at 6.994 MeV excitation energy. The experimental Coulomb energy differences, obtained by comparison with the isobaric analog states in its mirror (50)Cr, confirm the qualitative interpretation of the backbending patterns in terms of successive alignments of proton and neutron pairs. A quantitative agreement with experiment has been achieved by exact shell model calculations, incorporating the differences in radii along the yrast bands, and properly renormalizing the Coulomb matrix elements in the pf model space.