Search results for "Moment of inertia"
showing 10 items of 45 documents
Moments of inertia of nuclei in the rare earth region: A relativistic versus nonrelativistic investigation
2000
A parameter free investigation of the moments of inertia of ground state rotational bands in well deformed rare-earth nuclei is carried out using Cranked Relativistic Hartree-Bogoliubov (CRHB) and non-relativistic Cranked Hartree-Fock-Bogoliubov (CHFB) theories. In CRHB theory, the relativistic fields are determined by the non-linear Lagrangian with the NL1 force and the pairing interaction by the central part of finite range Gogny D1S force. In CHFB theory, the properties in particle-hole and particle-particle channels are defined solely by Gogny D1S forces. Using an approximate particle number projection before variation by means of the Lipkin Nogami method improves the agreement with the…
Very high rotational frequencies and band termination in73Br
2000
Rotational bands in ${}^{73}\mathrm{Br}$ have been investigated up to spins of $I=65/2$ using the EUROBALL III spectrometer. One of the negative-parity bands displays the highest rotational frequency $\ensuremath{\Elzxh}\ensuremath{\omega}=1.85\mathrm{MeV}$ reported to date in nuclei with $Ag~25.$ At high frequencies, the experimental ${\mathcal{J}}^{(2)}$ dynamic moment of inertia for all bands decreases to very low values, ${\mathcal{J}}^{(2)}l~10{\ensuremath{\Elzxh}}^{2}{\mathrm{MeV}}^{\ensuremath{-}1}.$ The bands are described in the configuration-dependent cranked Nilsson--Strutinsky model. The calculations indicate that one of the negative-parity bands is observed up to its terminatin…
Stable triaxiality at the highest spins in138Ndand139Nd
1999
The nuclei ${}^{138}\mathrm{Nd}$ and ${}^{139}\mathrm{Nd}$ have been studied at very high spins via the ${}^{48}\mathrm{Ca}{+}^{94}\mathrm{Zr}$ reaction. Several new rotational bands were observed, four in ${}^{138}\mathrm{Nd}$ and two in ${}^{139}\mathrm{Nd}.$ The ${J}^{(2)}$ moments of inertia calculated from the observed $\ensuremath{\gamma}$-ray energies are very small and almost constant, indicating that these bands are triaxial. Cranked Nilsson-Strutinsky calculations reproduce the general behavior of the bands, supporting this interpretation and suggesting an approximately constant $\ensuremath{\gamma}$ value of $\ensuremath{\sim}+35\ifmmode^\circ\else\textdegree\fi{}$ over a large s…
Quadrupole variation of projected spectra of even Ti isotopes
1975
In the present work we study the dependence of projected good $J$ states on the quadrupole moment. In order to achieve this, the quadrupole-moment-depenent generalized deformed BCS (DBCS) wave functions have been computed after minimizing the constrained Hamiltonian ${H}_{q}=H\ensuremath{-}\ensuremath{\lambda}N\ensuremath{-}\ensuremath{\mu}Q$. The calculation assumes the existence of a $^{40}\mathrm{Ca}$ spherical core. The two body residual interaction between the valence nucleons is determined by using the $^{42}\mathrm{Sc}$ spectrum for the $T=0$ force and the $^{49}\mathrm{Ca}$ spectrum for the $T=1$ force. The result of the calculation shows that the projected spectra in general cannot…
Spontaneous fission lifetimes from the minimization of self-consistent collective action
2013
The spontaneous fission lifetime of 264Fm has been studied within nuclear density functional theory by minimizing the collective action integral for fission in a two-dimensional quadrupole collective space representing elongation and triaxiality. The collective potential and inertia tensor are obtained self-consistently using the Skyrme energy density functional and density-dependent pairing interaction. The resulting spontaneous fission lifetimes are compared with the static result obtained with the minimum-energy pathway. We show that fission pathways strongly depend on assumptions underlying collective inertia. With the non-perturbative mass parameters, the dynamic fission pathway become…
INFLUENCE OF UNCERTAINTIES ON PD TUNING
2013
The aim of this work is to present a method for tuning the parameters of PD controller under the influences of the uncertainties, in order to stabilize the position of a rotor supported by active magnetic bearings (AMBs). The uncertainties are relative to mass, transverse and polar moment of inertia of the rotor. The introduction of the uncertainties is due to an incomplete modeled dynamic of the system or in the case the system being subjected to a parametric variation. The presence of the uncertainties produces a set of differences among the values of the output. Poles displacement method is used to reach the asymptotically stability condition characterized by a periodic oscillation durin…
Observation of an Intense Quasicontinuum of Superdeformed Rotational Transitions inEu143
1996
Quasicontinuum spectra in coincidence with transitions belonging to the different potential wells of {sup 143}Eu are studied with an increasing number of coincidence folds. An intense bump of rotationally correlated transitions is observed to develop in the high spin region. Fold distributions, angular anisotropies, moment of inertia determinations, and lower limits of lifetimes as a function of the rotational frequency show that the bump originates from highly collective rotationally damped {ital E}2 transitions generated by superdeformed states. {copyright} {ital 1996 The American Physical Society.}
Multidimensional Skyrme-density-functional Study of the Spontaneous Fission of 238U
2015
We determined the spontaneous fission lifetime of 238U by a minimization of the action integral in a three-dimensional space of collective variables. Apart from the mass-distribution multipole moments Q20 (elongation) and Q30 (left–right asymmetry), we also considered the pairing- fluctuation parameter λ2 as a collective coordinate. The collective potential was obtained self-consistently using the Skyrme energy density functional SkM∗ . The inertia tensor was obtained within the nonperturbative cranking approximation to the adiabatic time-dependent Hartree–Fock– Bogoliubov approach. The pairing-fluctuation parameter λ2 allowed us to control the pairing gap along the fission path, which sign…
Cluster rotational bands in 11B
2016
Differential cross-sections of 11B+α inelastic scattering at E(α) = 65 MeV leading to most of the known 11B states at excitation energies up to 14 MeV were measured [1]. The data analysis was done using Modified diffraction model (MDM) [2] allowing determining radii of excited states. Radii of the states with excitation energies less than ∼ 7 MeV coincide with the radius of the ground state with an accuracy not less than 0.1 - 0.15 fm. This result is consistent with traditional view on shell structure of low-lying states in 11B. Most of the observed high-energy excited states are distributed among four rotational bands. Moments of inertia of band states are close to the moment of inertia of…
Reference-point-independent dynamics of molecular liquids and glasses in the tensorial formalism.
2002
We apply the tensorial formalism to the dynamics of molecular liquids and glasses. This formalism separates the degrees of freedom into translational and orientational ones. Using the Mori-Zwanzig projection formalism, the equations of motion for the tensorial density correlators S(lmn,l'm'n')(q-->,t) are derived. For this we show how to choose the slow variables such that the resulting Mori-Zwanzig equations are covariant under a change of the reference point of the body fixed frame. We also prove that the memory kernels obtained from mode-coupling theory (MCT) including all approximations preserve the covariance. This covariance makes, e.g., the glass transition point, the two universal s…