Simple Rotational Model Research Articles

A Hysteresis Model for Antiferroelectric SmCA* Phases

In this paper, we shall present a simple irreversible rotation model with a couple of polarization vectors to account for the hysteretic phenomena in SmCA* phases. From a numerical calculation, a double hysteresis curve was found in antiferroelectric SmCA* phase, whereas a single curve was found in the ferroelectric SmC* phase. Remarkably it is found that there exists a direct ferroelectric-ferroelectric transition under a sinusoidal electric field with a sufficiently large amplitude and high frequency in qualitative agreement with experimental findings.

Vibronic interactions and normal coordinate rotation in quinizarin

The vibronic coupling and normal coordinate mixing of nontotally symmetric vibrations are investigated in quinizarin. The applicability of a simple normal coordinate rotation model and first-order Herzberg-Teller approximation are tested. They appeared to work for harmonic vibrations and failed to function for anharmonic ones.

Ridge lifetimes in 167,168Yb

A Doppler shift attenuation technique has been applied to the quasi continuum ridge structure of the deformed nuclei 167,168Yb populated by the reaction 124Sn + 48Ca. The Doppler shift of the ridge is analysed and compared to a simple rotational model for the feeding transitions and to more detailed Monte Carlo simulations. The data show a reduction of the rotational strength compared to the low spin E2 decay and point to strong alignment effects around spin 40ħ.

Rotational collectivity in shell-model wave functions for A=20-28 nuclei.

Results of shell-model calculations for A=20--28 nuclei are examined for manifestations of collective rotational structure. The calculations use the full set of 0${d}_{5/2}$-1${s}_{1/2}$-0${d}_{3/2}$ configurations and an empirical Hamiltonian which yields a comprehensive reproduction of A=18--38 spectroscopy. The shell-model eigenvalues and the electric quadrupole matrix elements calculated from the shell-model eigenfunctions are treated as pseudodata from which the parameters of the simple rotational model are extracted. These analyses reveal extended groups of model levels in several nuclei which can be characterized in terms of well-defined moments of inertia and stable intrinsic quadrupole deformations. The ``bandlike'' structure of these groups persists, with diminishing intensity, to the largest values of total angular momentum which can be generated within the sd-shell space for these nuclei. Other sd-shell nuclei which are sometimes considered as ``rotational'' exhibit some fragmentary evidence for rotational collectivity in the present analyses, but the characteristics of band structure are not sustained over extended sequences of levels.

The Medina Wrench: a key to the kinematics of the central and eastern Mediterranean over the past 5 Ma

The Medina Wrenth in the central Mediterranean is a transform fault connecting the plate collision in northwest Africa and northern Sicily with that occurring at the Aegean plate boundary, south of Greece. The more than 800 km long crescent-shaped wrench zone is currently seismically quiet but exhibits major deformation since 5 Ma within a belt 30–100 km wide. It forms the southern boundary of two microplates moving eastward with respect to Africa and Europe. A simple plate rotation model constrained by recent paleomagnetic data indicates that a continental Iblean microplate and a hybrid continental/oceanic Ionian microplate, separated along the Malta Escarpment, have rotated anticlockwise by 11° and 12°, respectively, around poles in southern Italy. These rotations involved some 100 km of dextral eastward movement relative to Africa of the Ionian Basin north of the Medina Wrench since 5 Ma. Combining the published 26° clockwise rotation of the Peloponnesus and northwest half of the Aegean with the 12° anticlockwise rotation of the Ionian microplate results in (a) a 99% agreement between the length of the seismic Benioff Zone beneath Greece and the total convergence of the microplates, and (b) an average rate of convergence across the Aegean plate boundary southwest of the Peloponnesus of 6.6 ± 1cm a −1 since the Miocene. Relative motion between microplates in a collision zone thus may be as much as 6 times faster than convergence between the major plates which spawned them, and they can be considered rigid to the first order over the time span involved.

Coupled mode analysis for magnetoelastic amorphous metal sensors

A simple dynamic dipole rotation model is developed for a single domain of a magnetostrictive amorphous metal. The equations of motion for the coupled magnetization and strain modes are presented. The resultant 2×2 dynamic susceptibility is useful in characterizing the performance of metallic glass based sensors. As an example, the stress and field dependence to the dynamic response of a fiber optic DC magnetometer is investigated.

Profile analysis of infrared absorption of NH stretching band

The shape of the infrared NH stretching band of N-methyl aniline in different solvents has been studied. Carbon tetrachloride, tetrachloroethylene, carbon disulfide, benzene, anisole, chloroform, dioxane and di-n-butyl ether were used as solvents. Band shapes observed show self-association of N-methyl aniline in dioxane, di-n-butyl ether and chloroform solutions. Moments analysis and time autocorrelation function calculations have been performed. The frequencies of the band maximum are more sensible to the solvent than the half band width and the band shape. Moments values depend strongly on the integration interval. The correlation function shows non-exponential decays in a short time range (0–0.16 ps) for any solutions, and this indicates that the molecular motions do not obey a simple rotational diffusion model. Exponential decays show at times longer than 0.16 ps. Relaxation times are linearly related with the solvents viscosity.

Solvent influence on the carbonyl stretching band shape of ethyl trifluoroacetate

The solvent influence on the shape of the carbonyl stretching band of ethyl trifluoroacetate has been studied, Nine infrared solvents were used:cyclohexane, n-hexane, di-n-butylether, 1,2-dichloroethane, carbon tetrachloride, tetrachloroehtylene, carbon disulfide, acetonitrile and chloroform, Moment analysis and time correlation function calculation have been performed. The frequency of the band maximum is more sensible to the solvent than the half band width, the band shape and the absolute intensity. The correlation functions show non-exponential decays in a short time region (0-0,4 ps) for any solutions, and this indicate that the molecular motions do not obey a simple rotational diffusion model. Exponential decays are shown at times longer than 0,4 ps,. Relaxation time and solvent viscosity have a quite linear relationships, but 1,2-dichloroethane and chloroform solutions follow a different behaviour.

Rotational isomeric model of the coil stretching transition of semiflexible polymers in elongational flow

A simple rotational isomeric-type model of polymers in elongational flows is developed and used to analyze the coil stretching and chain retraction as a function of polymer and flow parameters. The results are in agreement with available experimental data on dilute polymer solutions in strong elongational flows.

13C-NMR Studies on Conformational Equilibria in Isopropyl Methyl Ether

Abstract The energy difference between the two rotational isomers, i.e., Cs and C1, of isopropyl methyl ether has been elucidated from the observed vicinal 13C-1H coupling constant. The conventional Gutowsky method based on the simple rotational isomeric state model tends to give an underestimate, especially when the energy difference is large. A more elaborate treatment, which takes account of the overall profile of the torsional potential energy curve, has been attempted. Adoption of JT=11.0–12.0 Hz for the trans coupling gave a value of 2.2±0.2 kcal mol−1 for the energy difference Ecs–Ec1. This result is consistent with the range (2.4±0.6 kcal mol−1) estimated by the matrix-isolation method as reported by Nakata et al.

Rotational properties of shell-model states infp-shell nuclei

The relation between the microscopic shell model and the collective rotor model is investigated. As the first step an extensive shell-model calculation is performed on about twentyfp-shell nuclei with massA=52–60. It turns out that, with the model space and the effective interaction chosen, the shell model is well able to reproduce the experimental data in this mass region. As the second step the shell-model wavefunctions are used to calculate energies, electromagnetic moments and transition rates of states with spin up toJ=16. As the third step the observables calculated with the shell model are used to investigate whether these microscopic results can be reproduced by a simple rotational model. About twenty pure axially symmetric rotor bands, generated by the shell model, could be localized. Their properties are presented and discussed.

Photodissociation of vibrationally excited CH 3Br

A two-step laser photodissociation technique is used to study the UV photodissociation of vibrationally excited CH 3Br. The absorption by CH 3Br of coincident lines of the 10.6 μm CO 2 laser is measured as a function of laser fluence and CH 3Br pressure. The results are compared with calculations based on spectroscopic parameters for the CH 3Br( v 6 0 → 1) absorption band and a simple rotational relaxation model. Subsequent photodissociation by a variably delayed UV laser pulse probes the effect of this vibrational excitation (and collisional vibrational energy transfer) on the UV photodissociation cross section.

Studies of molecular motions and vibrational relaxation in acetonitrile

Far-infra-red spectra in the 2–200 cm-1 region of dilute solutions of CH3CN in CCl4 solution have been employed to test the various analytical models available for the description of rotational motions of a symmetric top dipole in the liquid phase. It is found that none of the various approximants of the Mori continued fraction description of reorientational correlation function fit the experimental data satisfactorily. This implies that, although the data (from this and other techniques) may appear to be properly described by a simple rotational diffusion model at long times, the short time dynamics are too complicated to be reproduced even by much more sophisticated models. The data are able to clearly discriminate between the various models tried and, in addition, give valuable information about the nature and extent of the mean square torques acting on the probe molecule.

Shell structure of collective states inFe56,Fe58, andFe60

Conventional shell-model calculations of the iron isotopes with $A=56\ensuremath{-}60$ are discussed. The calculated level spectra are in good agreement with experiment. The calculations of $E2$ observables are in reasonable agreement with experiment when added effective charges of $1.0e$ are used for both neutrons and protons. The neutron effective charge is significantly different from one appropriate ($1.9e$) for $^{56}\mathrm{Ni}$. There is a strong state dependence in the effective $M1$ operator, and calculations of $M1$ observables are in general disagreement with experiment. An analysis of the structure of ground-state bands and yrast levels is made in terms of a simple rotational model. In all even isotopes, the intrinsic quadrupole moments in the ground-state "band" shrink dramatically with increasing $J$. There is evidence of a band crossing in all three even isotopes, but no evidence is found for an abrupt shape change in the ground-state bands of these nuclei. It is concluded that no simple rotational model gives a good description of the low-lying states of the iron isotopes.NUCLEAR STRUCTURE $^{56}\mathrm{Fe}$, $^{57}\mathrm{Fe}$, $^{58}\mathrm{Fe}$, $^{59}\mathrm{Fe}$, $^{60}\mathrm{Fe}$, calculated levels. $^{56}\mathrm{Fe}$, $^{58}\mathrm{Fe}$, $^{60}\mathrm{Fe}$, calculated $B(M1)$, $B(E2)$, $\ensuremath{\mu}$, branching ratios. Shell model, Vervier interaction, Horie-Ogawa interaction, effective operators. Comparison with experiment and rotational model.

Some insight into the structure of the nuclei 19F, 19Ne, 21Ne, 21Na, 23Na and 23Mg through the generator coordinate method and the projected Hartree-Fock method

Structures of two sets of mirror nuclei 19Ne, 21Na, 23Mg and 19F, 21Ne, 23Na were studied comparatively by means of the electromagnetic properties of the even-parity states, calculated with the generator coordinate method and with mixing of projected Hartree-Fock determinants. The present results are compared with those of complete diagonalization. In particular, collective features of these nuclei are investigated by comparing the various microscopic results with the predictions of the simple rotational model.

Neutron quasi-elastic scattering of n-nonadecane

A neutron quasi-elastic investigation of the plastic phase of a randomly orientated sample of n-nonadecane shows good agreement with a simple continuous rotational diffusion model of the molecule about its long axis. No quasi-elastic broadening is observed in the lower temperature phase.

Neutron scattering from ammonium salts. I. Coexisting phases in NH4I and NH4+dynamics in phase I and II

Neutron quasi-elastic and elastic scattering experiments from NH4I are reported in the temperature range 213K-300K. It is shown that both while cooling and heating, one obtains an NaCl phase coexisting with low-temperature phases. This calls for great care in interpreting any data on NH4I in this temperature range. The reorientation times for NH4+ ions in the CsCl phase are determined. In the NaCl phase it is shown that a simple rotational diffusion model does not describe NH4+ reorientations properly.

Evidence for a Nonrotational Interpretation of〈0+||M(E4)||4+〉inHf180

Angular distributions for the reaction $^{180}\mathrm{Hf}(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}})$ were measured for laboratory $\ensuremath{\alpha}$-particle energies of 21 and 24 MeV. Data were obtained for ${0}^{+}$, ${2}^{+}$, ${4}^{+}$, and ${6}^{+}$ members of the ground-state rotational band. Data for the ${4}^{+}$ state show unambiguously that $〈{0}^{+}|\ifmmode\times\else\texttimes\fi{}|M(E4)||{4}^{+}〉$ is large and negative. Data for the ${6}^{+}$ state are not well-fitted by rotational-model coupled-channels calculations. These results may indicate that the interpretation of the $E4$ matrix element as arising from a static ${\ensuremath{\beta}}_{4}$ deformation in the framework of the simple rotational model is incorrect.

Elastic and Raman scattering of 8.5–11.4 MeV photons from 175Lu and 181Ta

Differential cross sections for elastic and inelastic Raman scattering from 175Lu and 181Ta were measured. Five photon energies between 8.5 and 11.4 MeV were used and were obtained from the (n, γ) reaction on Ni and Cr using thermal neutrons. The results are compared with calculations using a modified simple rotator model (SRM) of the giant dipole resonance (GDR) in which the effect of Delbrück scattering was incorporated. In general, fair agreement between theory and experiment is obtained. A new set of GDR parameters is extracted, based on photon scattering data and, as expected, yield better agreement between experimental and predicted cross sections.

Elastic and Raman scattering of 8.5–11.4 MeV photons from 159Tb, 165Ho and 237Np

Differential cross sections for elastic and inelastic Raman scattering from the deformed heavy nuclei 159Tb, 165Ho and 237Np were measured at five energies between 8.5 and 11.4 MeV. Angular distributions at four angles between 90° and 140° for both elastic and inelastic scattering at 9.0 and 11.4 MeV were also measured. The monoenergetic photons were obtained from thermal neutron capture in Ni and Cr. All the angular distributions and the elastic and Raman scattering at the higher energies are in good overall agreement with theoretical predictions. The theory is based on a modified simple rotator model of the giant dipole resonance in which the effect of Delbrück scattering was included. A trend of both the elastic and Raman scattering at lower energies to be stronger than expected are suggested by the data. However, the ratio between the Raman and elastic scattering seem to be in good agreement with theory throughout the whole energy range. This shows that there is no need to introduce a direct nonresonant component to the imaginary part of the elastic scattering amplitude to explain the experimental data.