Dynamic Moment Of Inertia Research Articles

Variation of moments of inertia with angular momentum and systematics of bandhead moments of inertia of superdeformed bands

The variation of the kinematic and dynamic moments of inertia and the bandhead moments of inertia ${J}_{0}$ systematics of superdeformed (SD) bands in the $A\ensuremath{\sim}190$ region are investigated, which turns out to be helpful in the spin prediction of SD bands. The spins of about 70 SD bands in the $A\ensuremath{\sim}190$ region are predicted by these approaches in combination with the usually adopted best-fit method. The ${J}_{0}$ systematics seems to be very useful to the understanding of the properties of excited SD bands and the implication of identical SD bands.

Enhanced deformation in light Pr nuclei

We observe for the first time rotational bands of enhanced deformation (ED) in 127 Pr and 128 Pr, and suggest that these bands are built upon πg 9/2 ( [404] 9 2 ) in 127 Pr and on the πg 9/2 νh 11/2 orbitals in 128 Pr. These are the lightest isotopes of Pr for which ED bands have been observed. A contrasting trend in the dynamical moments of inertia ( J (2) ) versus N is observed at low frequencies for the “normal-deformed” πh 11/2 and “enhanced-deformed” πg 9/2 bands of 127 –131 Pr both experimentally and in self-consistent Woods-Saxon calculations. The trends in J (2) and β 2 are correlated with a decreasing probability for pair scattering into the deformation-driving νh 9/2/ f 7/2 ( [541] 1 2 ) orbital.

Intrinsic proton states around the superdeformed shell closureZ=80

High spin states in ${}^{193}\mathrm{Tl}$ have been populated by the ${}^{181}\mathrm{Ta}{(}^{16}\mathrm{O},6n)$ reaction at 110 MeV and \ensuremath{\gamma}-ray spectroscopy was performed using the EUROGAM II array. In addition to the two known superdeformed (SD) bands, three new superdeformed bands have been identified. The dynamic moments of inertia of two of these new bands display a sudden and opposite change of slope and two of them have identical transition energies within 2 keV. The behavior of their dynamic moments of inertia and their \ensuremath{\gamma} transitions allowed us to propose configurations for the proton orbitals involved around the SD shell closure $Z=80.$ The intrinsic proton states identified are the two signature partners of the $[411]1/2$ and the negative signature of the $[651]1/2$ orbitals. Their properties are compared to the predictions of two theoretical calculations.

Quadrupole moment of superdeformed bands in 151Tb

The quadrupole moments of the first two superdeformed (SD) bands in the nucleus 151Tb have been measured with the Doppler Shift Attenuation Method (DSAM) using the EUROGAM γ-ray spectrometer. The first excited band (B2) is identical to the yrast SD band of 152Dy in terms of dynamical moments of inertia and γ-ray energies. The measured relative quadrupole moments of the yrast band (B1) with respect to the band B2 are nicely reproduced by self-consitent Hartree-Fock calculations. The variation of the Q0 value at the bottom of the yrast band suggests a large admixture between wave functions in the normal and the SD wells. This could explain the rather high deexcitation spin for the yrast band.

Description of Superdeformed Triaxial Band in 163Lu

Using triaxial-particle-rotor model, the γ-transition energies, kinematic and dynamic moments of inertia and the transition quadrupole moments for π[660 1/2] band in 163Lu are calculated and compared with the observed data. The results prove that this band is a superdeformed triaxial band.

Extended spectroscopy in the superdeformed well of148,149Gdnuclei

A high statistics experiment performed on Gd nuclei with the use of the EUROGAM II array resulted in the discovery of twelve new superdeformed (SD) bands. Three of them have been assigned to ${}^{148}\mathrm{Gd}$ and seven to ${}^{149}\mathrm{Gd}$ giving a total of thirteen SD bands now known in this last nucleus. The close relationship in transition energies between these bands and those in neighboring nuclei has been used to suggest configurations. Most of the new bands exhibit more or less pronounced irregularities in their dynamical moments of inertia with consequences on their identities with other bands.

Superdeformation in145Sm

Two superdeformed bands have been observed in the nucleus {sup 145}Sm in an experiment performed with the Gammasphere multidetector array. One of these bands demonstrates a sudden rise in its dynamic moment of inertia at low frequency which may be related to the interaction between N=6 Nilsson orbitals at the Fermi surface. The other band has a moment of inertia identical to the yrast band of {sup 149}Gd, making it the fourth case in the A{approx_equal}150 mass region of identical bands in nuclei differing by an {alpha} particle. {copyright} {ital 1998} {ital The American Physical Society}

Lifetime measurements of the rotational quasi-continuum transitions in 163 Tm

Abstract The lifetime of the unresolved transitions forming the rotational quasi-continuum spectra has been measured in 163 Tm using the Doppler shift attenuation technique. Spectra associated to different values of the coincidence folds, angular anisotropies and the dynamical moment of inertia were also obtained from the present experiment. The Doppler shift has been measured for discrete transitions, for the ridge structures in E γ 1 × E γ 2 spectra and for the rotational E2 bump in one dimensional spectra. The data were compared to the theory using a simulation model which makes use of microscopically calculated levels and transition probabilities. Above 1300 keV the results indicate collectivity with lifetime faster than 10 −14 s, while at lower E γ the results are well described by predictions with B (E2) = 400 WU.

An empirical analysis of superdeformed bands: A semiclassical view

Abstract An empirical analysis of the superdeformed (SD) bands is presented. The analysis is backed by the dynamical features of the cranking model [Jain et al., Phys. Lett. B 370 (1996) 1] and the particle rotor model [Jain et al., Phys. Lett. B 392 (1997) 243] recently obtained from a semi-classical approach. It is found that the weak oscillations in the angular momentum vs. gamma ray energy plots (as also observed in the data) would be absent if the nonlinearity of the model is ignored. A linear fit to the experimental data, based on this premise, therefore leads to an average value of the moment of inertia and the aligned angular momentum. The values of the moment of inertia are found to be very close to the rigid body values. Also the alignment is found to be mostly negative in accordance with the trend predicted by theory. Recently observed downturn in the dynamical moment of inertia is shown to be related to the saturation of the aligned angular momentum.

Cranked relativistic mean field description of superdeformed rotational bands

The cranked relativistic mean field theory is applied for a detailed investigation of eight superdeformed rotational bands observed in $^{151}$Tb. It is shown that this theory is able to reproduce reasonably well not only the dynamic moments of inertia $J^{(2)}$ of the observed bands but also the alignment properties of the single-particle orbitals.

High-spin spectroscopy of52 116Te

High-spin states in the nucleus {sup 116}Te have been studied with the reaction {sup 64}Ni({sup 56}Fe,2p2n) at 236 MeV using an early implementation of the Gammasphere array. Three rotational bands extending to spins I{approximately}(25{minus}42){h_bar} and excitation energies E{sub ex}{approximately}(11{minus}24) MeV have been identified and connected to known low-lying states. In the most extended band, a gradual decrease in the dynamic moment of inertia J{sup (2)} with increasing rotational frequency has been observed and interpreted as evidence for smooth band termination. Several energetically favored states based on aligned single-particle configurations also have been found to coexist with weakly deformed collective structures at low spins. {copyright} {ital 1997} {ital The American Physical Society}

Exponential model with pairing attenuation applied to superdeformed nuclei in theA∼190region

42 superdeformed (SD) bands, which have a pronounced increase in the dynamic moment of inertia ${\mathcal{J}}^{(2)}$ with rotational frequency $\ensuremath{\Elzxh}\ensuremath{\omega}$ in the $A\ensuremath{\sim}$190 region, are studied using the exponential model with pairing attenuation. The level spins are suggested and the parameters ${\mathcal{J}}_{0}$ and ${\ensuremath{\Delta}}_{0}$ are determined for these bands. The excellent agreement between the calculated ${E}_{\ensuremath{\gamma}}$ and the observed ${E}_{\ensuremath{\gamma}}$ gives good support to the model. The parameters ${\mathcal{J}}_{0}$, ${\ensuremath{\Delta}}_{0}$ and the band head moment of inertia ${\mathcal{J}}_{\mathrm{b}.\mathrm{h}.}$ show evident odd-even effects which may indicate different intrinsic structure in the studied SD nuclei.

Band structure of superdeformed bands in odd-A Hg nuclei

Through particle-rotor model, band structure of superdeformed bands in odd-A Hg nuclei is analysed. An overall and excellent agreement between the calculated and observed kinematic and dynamic moments of inertia is obtained. The electromagnetic transition properties of SD bands can be used to identify the configuration with certainty.

A comparison of the known SD bands in the mass A≈80 region

The mass A≈80 region is now firmly established as the newest region of superdeformation, with up to 11 nuclei exhibiting as many as 21 superdeformed bands. The dynamic moments of inertia of these bands reveal a variety of interesting features, such as superdeformed band crossings and the first pair of identical superdeformed bands in the mass A≈80 region. Cranked shell model calculations have been performed and the bands are interpreted in terms of the number of high-N intruder orbitals occupied. The differences in dynamic moments of inertia and the proposed single particle configurations are discussed.

Nonlinear dynamics of particle rotor model and superdeformed bands

We present a complete discussion of the nonlinear dynamics of the particle-rotor for single- j configuration. We carry out a semiclassical quantization about the various fixed points and present numerical results for the bands built at the stable fixed points c ±. These bands are observed to be rotational in nature and exhibit a weak oscillation in gamma ray energies. Results are also presented for alignment and dynamical moment of inertia. A comparison with the experimental data on superdeformed bands reveals several common features.

Superdeformed band in 155Dy: Where does the "island" of superdeformation end?

A superdeformed band of 15 transitions has been found in the $^{155}\mathrm{Dy}$ nucleus. The measurement was performed with a backed target and the large deformation was inferred from the measured Doppler shifts. The new band displays an intensity pattern much different from typical superdeformed bands in this mass region. The dynamic moment of inertia is essentially identical to that of band 1 in $^{153}\mathrm{Dy}$ and is somewhat larger than those of the yrast superdeformed bands in $^{152,154}\mathrm{Dy}$, suggesting that the associated configuration has an additional N=7, ${\mathit{j}}_{15/2}$ intruder orbital occupied with respect to the $^{154}\mathrm{Dy}$ core. \textcopyright{} 1996 The American Physical Society.

M1 transitions between superdeformed states in

Using a triaxial-particle-rotor model, the quadrupole and dipole transition energies, kinematic and dynamic moments of inertia, electromagnetic transition probabilities and the relative intensity of the E2 -transitions are calculated for superdeformed bands in . A strong perturbation effect of rotation on transition energies and M1 and E2 transitions of superdeformed states is investigated. The total M1 transitions, enhanced by internal conversion, are expected to compete strongly with the E2 -ray at low spins in the superdeformed nucleus.

Collective and quasiparticle excitations in superdeformed 190Hg.

Superdeformed (SD) states of $^{190}\mathrm{Hg}$ have been studied with the Eurogam Phase 2 \ensuremath{\gamma}-ray spectrometer using the $^{160}\mathrm{Gd}$${(}^{34}$S,4n) reaction. Two new excited SD bands have been found and identified as belonging to this nucleus, bringing the total number of SD bands in $^{190}\mathrm{Hg}$ to 4. One of the new bands has a dynamic moment of inertia that is very similar to that of the yrast SD band of $^{190}\mathrm{Hg}$ and most other SD bands in the A\ensuremath{\sim}190 region. In contrast, the other band has a dynamic moment of inertia which is mainly constant as a function of rotational frequency and exhibits a dramatic increase at the lowest frequencies. The observed dynamic moments of inertia are compared with the results of random phase approximation calculations based on the cranked shell model. Finally, the known excited SD band has been extended towards lower frequencies and new transitions have been found linking this band to the yrast SD band. The extracted B(E1) values of the new linking transitions give further support for the possible octupole vibrational character of this band. \textcopyright{} 1996 The American Physical Society.

Description of superdeformed nuclei in the interacting boson model.

The interacting boson model is extended to describe the spectroscopy of superdeformed bands. Microscopic structure of the model in the second minimum is discussed and superdeformed bosons are introduced as the new building blocks. Solutions of a quadrupole Hamiltonian are implemented through the $1/N$ expansion method. Effects of the quadrupole parameters on dynamic moment of inertia and electric quadrupole transition rates are discussed and the results are used in a description of superdeformed bands in the Hg-Pb and Gd-Dy regions.

Alignment additivity in the two-quasiparticle superdeformed bands of 192Tl.

Four superdeformed bands have been confirmed in $^{192}\mathrm{Tl}$. Two of these bands have ${\mathcal{I}}^{(2)}$ dynamic moments of inertia which are nearly constant with rotational frequency \ensuremath{\Elzxh}\ensuremath{\omega}. The other two bands show the characteristic rise of ${\mathcal{I}}^{(2)}$ with increasing \ensuremath{\Elzxh}\ensuremath{\omega} seen in most superdeformed bands of the A = 190 region of superdeformation. From comparisons with the odd-A neighbors, it was found that the alignments of these bands relative to a $^{192}\mathrm{Hg}$ core can be accounted for from the additive contributions of the assigned quasiproton and quasineutron orbitals. \textcopyright{} 1996 The American Physical Society.