Angular Momentum Dependence Research Articles

Effect of Angular Momentum–Dependent Transparency on the Neutron-Nucleus Cross Section

We study the effect of the angular momentum dependence of the optical potential transparency on the neutron-nucleus cross section. In this work, we derive a functional form of the neutron-nucleus cross section with respect to spherical optical potential using the collision matrix and modify it. We also apply an analytical model (Ramsauer) to the square optical potential and the optical model using the TALYS 1.96 code to get the angular momentum–independent transparency and demonstrate the effect of the angular momentum dependence via comparison of two models. In this work, we calculate the neutron cross sections for 40 ≤ A ≤ 90 nuclei, with energies 100 MeV ≤ En ≤ 200MeV theoretically, the for ℓ ≠ 0 case. We find that the angular momentum dependence of the transparency treats good calculations of the neutron-nucleus cross section; a finite number of angular momentums will contribute appreciably to the nuclear reaction. The present study on smooth optical potential leads to useful insight into the mechanisms of neutron-induced reactions, particularly for medium nuclei at high energies.

Calculation of the half-life of proton radioactivity using the empirical formula depending on angular momentum

In this paper, considering the power of the daughter nuclear charge as a function of the orbital angular momentum taken away by the emitted proton, we propose a formula for the half-life of proton radioactivity. In this formula, we have three coefficients with orbital angular momentum dependence. Using experimentally measured half-lives for 8 proton emitters with [Formula: see text], 14 proton emitters with [Formula: see text] and 18 proton emitters with [Formula: see text], we have obtained the coefficients. The root mean square deviations of our formula respect to the experimental value are found 0.2514, 0.4442 and 0.1846 for emitters [Formula: see text], 2 and 5, respectively. We have compared our results with Sreeja formula, the semiempirical relation of Hatsukawa and theoretical models such as the Coulomb and proximity potential model (CPPM) and the Gamow-like model. The better agreement with experimental data was observed for our formula in comparison with other theoretical models and Sreeja and Hatsukawa formulas.

On the existence of a tight planar relation between stellar specific angular momentum, mass, and effective surface brightness for ALFALFA galaxies

ABSTRACT Measurements of the dependence of stellar specific angular momentum (j*) on stellar mass (M*) are presented for large samples of galaxies from the Arecibo Legacy Fast ALFA (ALFALFA) survey, spanning the stellar mass range ∼108–1011 M⊙. Accurate estimates of j* are generated using measurements of I-band effective radius and velocity width of the H i line profile. While the full sample (N = 3607) of galaxies yields a j*–M* relation with power-law index α = 0.404 ± 0.03, it is shown that various subsamples have indices that are very similar to the best literature results, yet with comparatively lower intrinsic scatters. A galaxy’s mean I-band surface brightness within its effective radius (<μeff>) is shown to significantly correlate with j*–M* scatter. A 3D plane fit to all N = 3607 galaxies in log10j*–log10M*–<μeff> space yields j* ∝ M0.589 ± 0.002 <μeff>0.193 ± 0.002 with scatter σ = 0.089 dex. <μeff>-selected subsamples of size up to N = 1450 yield power-law j*–M* relations mostly consistent with α = 0.55 ± 0.02 from the literature and with intrinsic scatter ranging from 0.083 to 0.129 dex. Thus, this paper presents new, highly accurate measurements of the j*–M* relation that can be used to better understand the important roles played by angular momentum in the formation and evolution of galaxies.

Reflection-asymmetric mode in the structure of heavy nuclei

The properties and description of the reflection-asymmetric mode in heavy nuclei are discussed. Two approaches based on the collective octupole degree of freedom and the mass asymmetry mode are presented. Angular momentum dependence of the parity splitting, phase transition in alternating parity rotational band, stabilization of the reflection-asymmetric deformation with angular momentum increase and the rigidity of the reflection-asymmetric deformation are considered.

Angular momentum of doubly magic 132Sn fission product: Experimental and theoretical aspects

Despite the numerous theoretical and experimental works published very recently, the way in which fission fragments acquire their angular momentum is still an open question. This angular momentum generation mechanism is important not only for improving our understanding of the fission process, but also for nuclear energy applications, since the angular momentum of fission fragments strongly impact the prompt gamma spectra and consequently the decay heat in a reactor. In this context, within the framework of a collaboration between the ‘Laboratoire de Physique Subatomique et Corpusculaire’ (LPSC, France), the ‘Institut Laue Langevin’ (ILL, France) and the CEA-Cadarache (France), an experimental program was developed on the LO-HENGRIN mass-spectrometer with the aim of measuring isomeric ratio of some fission products for different thermal-neutron-induced fission reactions. This paper will be focused on the results obtained for the spherical nucleus 132Sn following thermal-neutron-induced fission of both 235U and 241Pu targets. To further challenge the angular momentum generation models, 132Sn isomeric ratio (IR) was measured as a function of 132Sn fission product kinetic energy (KE). The angular momentum was determined by combining our experimental data with the calculations performed with the FIFRELIN Monte Carlo code. A clear angular momentum decrease with KE was observed for both reactions. Lastly, we investigate the dependence of the 132Sn angular momentum with the incident neutron energy, from thermal region up to 5 MeV (below the second-chance fission). For that, the four free available parameters in FIFRELIN are selected in order to reproduce the average prompt neutron multiplicity. In this way, the angular momentum is deduced for each neutron energy. These results are discussed in terms of the impact of the available intrinsic excitation energy at scission on the spin generation mechanism.

XGASS: the connection between angular momentum, mass, and atomic gas fraction in nearby galaxies

ABSTRACT We use a sample of 559 disc galaxies extracted from the eXtended GALEX Arecibo SDSS Survey to study the connection between baryonic angular momentum, mass, and atomic gas fraction in the local Universe. Baryonic angular momenta are determined by combining H i and H2 integrated profiles with 2D stellar mass surface density profiles. In line with previous work, we confirm that specific angular momentum and atomic gas fraction are tightly correlated, but we find a larger scatter than previously observed. This is most likely due to the wider range of galaxy properties covered by our sample. We compare our findings with the predictions of the analytical stability model developed by Obreschkow et al. and find that, while the model provides a very good first-order approximation for the connection between baryonic angular momentum, mass, and gas fraction, it does not fully match our data. Specifically, we find that at fixed baryonic mass, the dependence of specific angular momentum on gas fraction is significantly weaker, and at fixed gas fraction, the slope of the angular momentum versus mass relation is shallower than what was predicted by the model. The reasons behind this tension remain unclear, but we speculate that multiple factors may simultaneously play a role, all related to the fact that the model is not able to encapsulate the full diversity of galaxy properties in our sample.

Numerical Equilibrium Configurations and Quadrupole Moments of Post-Merger Differentially Rotating Relativistic Stars

Numerical simulations of binary neutron star mergers invariably show that, when a long-lived remnant forms, its rotation profile is never a simple decaying function of the radius but rather exhibits a maximum rotation rate shifted away from the center. This is in contrast to the usual differential rotation profile employed for the numerical modeling of axisymmetric equilibria of relativistic stars. Two families of rotation rate functions that mimic post-merger profiles were proposed by Uryū et al. (2017). In this work we implement Uryū’s profiles into the XNS code by Bucciantini and Del Zanna (2011) and we present novel equilibrium sequences of differentially rotating neutron stars. These are constructed by using three different equations of state, in order to study the dependence of mass, radius, angular momentum, and other important physical quantities, especially the quadrupole deformation and metric quadrupole moment, from the rotation properties.

Unraveling the vector nature of generalized space-fractional Bessel beams

We introduce an exact analytical solution of the homogeneous space-fractional Helmholtz equation in cylindrical coordinates. This solution, called the vector space-fractional Bessel beam (SFBB), has been established from the Lorenz gauge condition and Hertz vector transformations. We perform scalar and vector wave analysis focusing on electromagnetics applications, especially in cases where the dimensions of the beam are comparable to its wavelength $({k}_{r}\ensuremath{\approx}k)$. The propagation characteristics such as the diffraction and self-healing properties have been explored with particular emphasis on the polarization states and transverse propagation modes. Due to continuous order orbital angular momentum dependence, this beam can serve as a bridge between the ordinary integer Bessel beam and the fractional Bessel beam and, thus, can be considered as a generalized solution of the space-fractional wave equation that is applicable in both integer and fractional dimensional spaces. The proposed SFBBs provide better control over the beam characteristics and can be readily generated using digital micromirror devices, spatial light modulators, metasurfaces, or spiral phase plates. Our findings offer insights on electromagnetic wave propagation, thus paving a route towards applications in optical tweezers, refractive index sensing, optical trapping, and optical communications.

Axionlike dark matter clouds around rotating black holes

Numerical analysis of dark matter axion-like cloud in the vicinity of rotating black hole has been performed. The model where axion-like scalar field is non-trivially coupled to Maxwell field is studied in the spacetime of Kerr black hole in uniform magnetic field and in Kerr-Newman one. The dependence of scalar mass and black hole angular momentum on accumulation of axion dark matter cloud was given. It was revealed that condensation of the dark matter clouds is preferable for a very small mass of axion.

Rotating Filament in Orion B: Do Cores Inherit Their Angular Momentum from Their Parent Filament?

Abstract Angular momentum is one of the most important physical quantities that governs star formation. The initial angular momentum of a core may be responsible for its fragmentation, and can have an influence on the size of the protoplanetary disk. To understand how cores obtain their initial angular momentum, it is important to study the angular momentum of filaments where they form. While theoretical studies on filament rotation have been explored, there exist very few observational measurements of the specific angular momentum in star-forming filaments. We present high-resolution N2D+ ALMA observations of the LBS 23 (HH24-HH26) region in Orion B, which provide one of the most reliable measurements of the specific angular momentum in a star-forming filament. We find the total specific angular momentum (4 × 1020 cm2 s−1), the dependence of the specific angular momentum with radius (j(r) ∝ r 1.83), and the ratio of rotational energy to gravitational energy (β rot ∼ 0.04) comparable to those observed in rotating cores with sizes similar to our filament width (∼0.04 pc) in other star-forming regions. Our filament angular momentum profile is consistent with rotation acquired from ambient turbulence and with simulations that show cores and their host filaments develop simultaneously due to multi-scale growth of nonlinear perturbation generated by turbulence.

Excitation energy and angular momentum dependence of the nuclear level density parameter around A≈110

Neutron kinetic energy spectra in coincidence with low-energy $\ensuremath{\gamma}$-ray multiplicities have been measured around $A\ensuremath{\approx}110$ in the $^{16}\mathrm{O}+^{93}\mathrm{Nb}$ and $^{20}\mathrm{Ne}+^{93}\mathrm{Nb}$ reactions in a compound nuclear excitation energy range of $\ensuremath{\approx}90--140$ MeV. The excitation energy (temperature) dependence and the angular momentum (spin) dependence of the inverse level density parameter $k$ have been investigated by comparing the experimental data with statistical Hauser-Feshbach calculations. In contrast to the available systematic in this mass region, the inverse level density parameter showed an appreciable increase as a function of the excitation energy. The extracted $k$ values at different angular momentum regions, corresponding to different $\ensuremath{\gamma}$ multiplicities, also showed an overall increase with the average nuclear spins. The experimental results have been compared with a microscopic statistical-model calculation and found to be in reasonable agreement with the data. The results provide useful information to understand the variation of nuclear level density at high temperature and spins.

The use of oscillator-strength sum rules for evaluating the angular-momentum dependence of the blackbody-radiation-induced broadening and shift of Rydberg-state energy levels

First evaluations of the blackbody-radiation (BBR)-induced shift and broadening of highly excited Rydberg states were based on the account of only the first term of the expansion for the Planck’s distribution in powers of the ratio of the BBR-photon energy to the environmental thermal energy. The corresponding asymptotic expression for the shift is proportional to a sum rule for the oscillator strengths, which is identical for all states, independently of their principal and angular-momentum quantum numbers. The broadening appeared proportional to the sum of the oscillator-strength first moments, which is dependent on only the principal quantum number, being independent of the state’s angular momentum. In this article, we demonstrate that the account of higher-order terms of the Planck’s distribution expansion provides corrections revealing the dependence of asymptotic shift and broadening on the Rydberg-state principal and angular-momentum quantum numbers. The strongest corrections are observed for states with low angular momenta, in agreement with earlier performed numerical calculations. Sum rules for higher moments of oscillator strengths are used for evaluating the corrections for the BBR-induced broadening and shift of Rydberg-state energy levels in neutral atoms and ions of arbitrary nuclear charge Z.

Phonon rotoelectric effect

In crystals with time-reversal symmetry but without inversion symmetry, the phonon angular momentum can be generated by the temperature gradient, and it is called phonon thermal Edelstein effect. On the other hand, when both symmetries are broken and their product is conserved, the phonon angular momentum for any phonon modes at any wave vectors vanishes, and the phonon thermal Edelstein effect does not occur. In this paper, we propose another mechanism of generation of the phonon angular momentum. We show that in such crystals the electric field generates the phonon angular momentum, via the lattice distortion due to the electric field. This effect is in the same symmetry class with the magnetoelectric effect, and we call this effect phonon rotoelectric effect. We discuss the temperature dependence of the phonon angular momentum generated by the temperature gradient and by the electric field in the high- and the low-temperature limits.

Anomalous transport in a topological Wannier-Stark ladder

A dc (e.g. electric) field with commensurate lattice direction turns a single particle band structure in $d=3$ dimensions into an infinite set of equally spaced irreducible $(d-1)=2$-dimensional Wannier-Stark (WS) band structures that are spatially localized along the field direction. Particle transport is expected to be suppressed once the WS bands are gapped in energy. The topological character of the irreducible band structure leads to one-dimensional sets of boundary states which fill the energy gaps. As a result, eigenmodes are smoothly connected in energy and space and yield anomalous particle transport throughout the ladder. The number of chiral boundary modes can be tuned by the dc field strength and manifests through the distribution of dissipated energy and spatial motion, and the temperature dependence of angular momentum carried by particles.

Few-body structures in the mirror nuclei O11 and Li11

We investigate the dripline mirror nuclei, $^{11}$Li and $^{11}$O, located on the neutron and proton dripline, respectively. We calculate the lowest four states, $3/2^-$, $1/2^+$, $3/2^+$ and $5/2^+$, built on double occupancy in the nuclear $s_{1/2}$ and $p_{1/2}$ valence single-particle states. We use the hyperspherical adiabatic expansion method to solve the three-body problem for a frozen nuclear core surrounded by two identical nucleons. The four analogue states in $^{11}$O are obtained with precisely the same interactions as used for the four states in $^{11}$Li, except for addition of the Coulomb interaction from the charge of the substituted valence protons. Surprisingly the four energies deviate from each other only by less than a few hundred keV. Any of them could then turn out to be the ground state, due to the uncertainty related to the angular momentum and parity dependence of the three-body potential. Still, our calculations marginally favor the $1/2^+$ state. The structures of these four states in $^{11}$O deviate substantially from the analogue states in the mirror, $^{11}$Li.

On the Dependence of the Relativistic Angular Momentum of a Uniform Ball on the Radius and Angular Velocity of Rotation

In the framework of the special theory of relativity, elementary formulas are used to derive the formula for determining the relativistic angular momentum of a rotating ideal uniform ball. The moment of inertia of such a ball turns out to be a nonlinear function of the angular velocity of rotation. Application of this formula to the neutron star PSR J1614-2230 shows that due to relativistic corrections the angular momentum of the star increases tenfold as compared to the nonrelativistic formula. For the proton and neutron star PSR J1748-2446ad the velocities of their surface’s motion are calculated, which reach the values of the order of 30% and 19% of the speed of light, respectively. Using the formula for the relativistic angular momentum of a uniform ball, it is easy to obtain the formula for the angular momentum of a thin spherical shell depending on its thickness, radius, mass density, and angular velocity of rotation. As a result, considering a spherical body consisting of a set of such shells it becomes possible to accurately determine its angular momentum as the sum of the angular momenta of all the body’s shells. Two expressions are provided for the maximum possible angular momentum of the ball based on the rotation of the ball’s surface at the speed of light and based on the condition of integrity of the gravitationally bound body at the balance of the gravitational and centripetal forces. Comparison with the results of the general theory of relativity shows the difference in angular momentum of the order of 25% for an extremal Kerr black hole.

Destruction of the orbital angular momentum in combined singular beams

This paper shows the dependence of the orbital angular momentum (OAM) of combined singular beams on the magnitude of the local perturbation in the holographic grating. In the absence of a perturbation of the holographic grating, the OAM acquires a maximum value numerically equal to the topological charge of the singular beam. With weak disturbances of a regular holographic grating, dips in the orbital moment appear. The depth of the dips increases rapidly with increasing disturbance. It is shown that even a weak perturbation of the lattice leads to a sharp increase in the contribution of partial beams with other topological charges. The reliability of the results obtained confirms the high degree of correlation of the intensity distribution of the original and reconstructed combined beams.

QCD evolution of the orbital angular momentum of quarks and gluons: Genuine twist-three part

We present the numerical solution of the one-loop QCD evolution equation for the genuine twist-three part of the orbital angular momentum (OAM) distributions of quarks and gluons inside a longitudinally polarized nucleon. This is based on the observation that the evolution is identical to that of the Efremov-Teryaev-Qiu-Sterman function for transverse single spin asymmetry. Together with the known evolution of the Wandzura-Wilczek part, the one-loop evolution of OAM distributions is now practically under control. We also study, for the first time, the scale dependence of the potential angular momentum defined as the difference between the Ji and Jaffe-Manohar definitions of OAM.

Deuteron wave function for Reid93 potential and polarization observables in elastic lepton–deuteron scattering

The elastic lepton–deuteron scattering was considered within the limits of zero lepton mass. The deuteron wave function in the coordinate representation for Reid93 potential was applied to numerical calculations. The angular-momentum dependence of values of the spin correlation coefficients [Formula: see text], [Formula: see text] and tensor asymmetries [Formula: see text], [Formula: see text], [Formula: see text] were evaluated in 3D format for Reid93 potential. These polarization observables are analyzed at different energies and scattering angles. The influence of the choice of the potential model and their nodes on the calculations of the polarization observables at a fixed scattering angle was taken into account. The application of the obtained values allows better explanation and illustration of the laws for the elastic lepton–deuteron scattering.

Nuclear pairing fluctuations and angular momentum dependence of superconductivity in 94Mo nucleus

The effects of thermal fluctuations on pairing properties of nuclei with inclusion of angular momentum have been investigated. To treat nuclei at finite temperature and angular momentum, we have extended the formalism in which the mean value of the gap parameter is used to obtain thermal properties of nuclei based on the BCS scheme [Z. Kargar and V. Dehghani, J. Phys. G, Nucl. Part. Phys. 40 (2013) 045108] let us name it MEGBCS. The results obtained for [Formula: see text] nucleus show the appearance of thermally assisted pairing correlations with increasing angular momentum. Also, the [Formula: see text]-shaped heat capacity found experimentally [K. Kaneko et al., Phys. Rev. C 74 (2006) 024325] and theoretically, interpreted as the second phase transition in mesoscopic systems, disappears with increasing angular momentum above a critical value. The nuclear level density of [Formula: see text] is calculated versus excitation energy at various values of total angular momentum. The total level density matches the experimental data closely.