SEARCH · Search NASA
Results for “Electromagnetic transitions”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Structure of the neutral pion and its electromagnetic transition form factor
Not Available
Electromagnetic recombination spectra at the quark-hadron phase transition
Not Available
Energy spectra and electromagnetic transition rates of {sup 160,162,164}Gd in the projected Hartree-Fock model
Band structure and electromagnetic properties of bands of {sup 160,162,164}Gd are studied theoretically upto high spin values using self-consisstent mean field theory. Predictions for the band structures are made. A K = 6{sup −} isomer at fairly low energy is predicted. Four quasi-particle bands involving i{sub 13/2} neutron and h{sub 11/2} protons are also studied.
Nucleon-to-Roper electromagnetic transition form factors at large Q 2
High-precision nucleon-resonance electroproduction data on a large kinematic domain of energy and momentum transfer have proven crucial in revealing novel features of strong interactions within the Standard Model and unfolding structural details of baryon excited states. Thus, in anticipation of new data reaching to unprecedented photon virtuality, we employ a quark-diquark approximation to the three-valence-quark bound-state problem to compute γ*p → R + and γ*n → R 0 transition form factors on Q 2 /m 2 N ϵ[0,12], where m N is the nucleon mass. Having simultaneously analyzed both charged and neutral channels, we also provide a quark-flavor separation of the transition form factors. Furthermore, the results should be useful in planning new-generation experiments.
Positive parity states and some electromagnetic transition properties of even-odd europium isotopes
The positive-parity low-spin states of even-odd Europium isotopes ({sup 151-155}Eu) were studied within the framework of the interacting boson-fermion model. The calculated positive low-spin state energy spectra of the odd Eu isotope were found to agree quite well with the experimental data. The B(E2) values were also calculated and it was found that the calculated positive-parity low-spin state energy spectra of the odd-A Eu isotopes agree quite well with the experimental data.
Quantum Monte Carlo Calculations of Electromagnetic Transitions in Light Nuclei
Recently, we presented ab initio quantum Monte Carlo calculations of magnetic moments and M1 transitions in A?10 nuclei, which include two-body meson-exchange currents' contributions of one- and two-pion range, derived from chiral effective field. These corrections are found to always improve the theoretical predictions, leading to a very good agreement with the experimental data. Here, we report on a study, carried out within the same framework, of M1 transitions in low-lying states of 8Be. We also present a number of E2 transition calculations, evaluated in impulse approximation, with emphasis on transitions involving the 8Be resonant excited states at ?3 MeV and ?11 MeV.
Quantum Monte Carlo calculations of electromagnetic transitions in light nuclei
Recently, we presented ab initio quantum Monte Carlo calculations of magnetic moments and M1 transitions in A <= 10 nuclei, which include two-body meson-exchange currents' contributions of one- and two-pion range, derived from chiral effective field. These corrections are found to always improve the theoretical predictions, leading to a very good agreement with the experimental data. Here, we report on a study, carried out within the same framework, of M1 transitions in low-lying states of 8Be. We also present a number of E2 transition calculations, evaluated in impulse approximation, with emphasis on transitions involving the 8Be resonant excited states at ~ 3 MeV and ~ 11 MeV.
Electromagnetic transitions in A lte10 nuclei including two-body xEFT currents
Recently, we presented ab initio quantum Monte Carlo calculations of magnetic moments and M1 transitions in A lte 9 nuclei, which include two-body chiral effective field theory meson exchange current contributions. The latter are found to always improve the theoretical predictions leading to a very good agreement with the experimental data. Here, we report on a preliminary study, carried out within the same framework, of electroweak transitions in additional A = 8 and A = 10 nuclear systems, with emphasis on transitions involving the isospin mixed states in 8Be at -16 MeV.
Spontaneous topological transitions of electromagnetic fields in spatially inhomogeneous C P -odd domains
Not Available
Application of Virtuality Distribution Formalism to Pion Transition and Electromagnetic Form Factors
We discuss application of newly developed formalism of virtuality distributions to pion-photon transition form factor and pion electromagnetic form factor.
Turbulent Transition in Electromagnetically Levitated Drops
Electromagnetic levitation (EML) is an important tool in materials research. Because a sample can be processed without contact with a container, experiments may be performed on high temperature, highly reactive, and undercooled liquid metals. Many of these experiments are affected by fluid flow in the sample, driven by the electromagnetic positioning force. Despite the importance of convection in these experiments, the transition to turbulence is not well understood in this system. However, we have observed a transition from laminar to turbulent flow in EML droplets in the course of microgravity experiments in TEMPUS on the Space Shuttle (STS-94). The transition occurs repeatably and over a narrow range of conditions. These experimental observations are compared with two competing theories about the transition to turbulence. Also, the results of a particle tracking study of the instabilities leading up to the transition to turbulence are presented.
Lifetime measurements probing collectivity in the ground-state band of 32 Mg
The signatures of inversion between normal and intruder configurations of particle-hole excitations across the N = 20 shell gap in the neutron-rich isotope 32 Mg have long been of keen interest. Electromagnetic transition rates in the ground-state band are key quantities that provide insights into collective properties associated with the contributions of the 2p2h and 4p4h intruder configurations. The combination of TRIPLEX, GRETINA, and the S800 spectrograph enables model-independent lifetime measurements to determine electromagnetic transition rates in rare isotopes. The reduced E2 transition rates in 32 Mg between the 2$^{+}_{1}$ and 0$^{+}_{1}$ states and between the 4$^{+}_{1}$ and 2$^{+}_{1}$ states have been measured, the latter representing the first experimental B(E2) value for this transition. Here, the B(E2) strengths indicate large collectivity and strong contributions from the 2p2h and 4p4h intruder configurations that may change with spin in the ground-state band of 32 Mg.
Precise Lifetime Measurements in Light Nuclei for Benchmarking Modern Ab-initio Nuclear Structure Models
A new generation of ab-initio calculations, based on realistic two- and three-body forces, is having a profound impact on our view of how nuclei work. To improve the numerical methods, and the parameterization of 3-body forces, new precise data are needed. Electromagnetic transitions are very sensitive to the dynamics which drive mixing between configurations. We have made a series of precise (< 3%) measurements of electromagnetic transitions in the A=10 nuclei {sup 10}C and {sup 10}Be by using the Doppler Shift Attenuation method carefully. Many interesting features can be reproduced including the strong α clustering. New measurements on {sup 8}Be and {sup 12}Be highlight the interplay between the alpha clusters and their valence neutrons.