Electroexcitation of magnetic dipole and other modes in46Ti and48Ti

Guhr, T.; Diesener, H.; Richter, A.; Jager, C. W. de; Vries, H. de; Huberts, P.K.A. de Witt

doi:10.1007/bf01290617

Cited by 13 publications

(49 citation statements)

References 54 publications

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“…00 52 3259 1995 The American Physical Society the q dependence of the theoretical cross section becomes very sensitive to the details of the microscopic wave function at higher momentum transfer q. Our theoretical M1 transition density of the 1 excitation at 3.78 MeV in Ti [11]describes well the corresponding experimental form factor [14] not only at low but also up to the highest measured momentum transfer q, f&~2 fm '. We were even able to predict [11]the form factor of the strongest M 1 excitation (at 7.2 MeV) in this nucleus in the same q range before the corresponding experimental data became available [15].The comparison with experiment can be seen in Fig.…”

Section: Motivationsupporting

confidence: 67%

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Competing electric and magnetic excitations in backward electron scattering from heavy deformed nuclei

1995

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Important E2 contributions to the (e, e ) cross sections of low-lying orbital Ml excitations are found in heavy deformed nuclei, arising from the small energy separation between the two excitations with I K= 2+1 and 1+1,respectively. They are studied microscopically in QRPA using DWBA. The accompanying E2 response is negligible at small momentum transfer q but contributes substantially to the cross sections measured at t/= 165' for 0.6(q,«(0.9 fm ' (40~E;~70 MeV) and leads to a very good agreement with experiment. The electric response is of longitudinal C2 type for (9~175 but becomes almost purely transverse E2 for larger backward angles. The transverse E2 response remains comparable with the M1 response for q, «) 1.2 fm ' (E;~100 MeV) and even dominant for E;)200 MeV. This happens even at large backward angles 0~175', where the M1 dominance is limited to the lower q region. PACS number(s): 25.30.Dh, 21.60.Jz, 27.70.+q I. MOTIVATION Inelastic electron scattering at a backward angle 0=180' was used by Peterson and co-workers [1,2] more than 30 years ago to study nuclear magnetic dipole (Ml) excitations at the linear accelerator in Stanford. The predominance of M 1 excitations in backward scattering is expected from qualitative considerations [2] of the (e,e ') cross section in the plane wave Born approximation (PWBA). The cross section can be decomposed in this case into longitudinal (Coulomb) and transverse (electric and magnetic) terms, multiplied by corresponding kinematical factors. The electric field of the incoming electron can have both longitudinal and transverse components, while its magnetic field is purely transverse. If the electron rest mass and the nuclear excitation energy can be neglected in comparison with the incident electron energy, which is often the case with low-lying excitations, the longitudinal kinematical factor vanishes for 0=180' and only transverse multipoles are excited by the inelastic scattering [3]. The (e, e ') cross section can be related further to the transition probability for photoabsorption through approximate considerations within the "virtual photon" method. One arrives in this way at the rough qualitative estimate [2] for dominant magnetic over electric transverse excitations (both of the same multipolarity). This property is due to the momentum transfer during electron scattering. It stands in contrast with the corresponding relationship for radiative excitation, where no momentum is transferred and the EL excitation is one order of magnitude stronger than the ML excitation (L stands for multipolarity). Electronic address: roland. noj arov uni-tuebingen. dẽ Electronic address: amand. faessler uni-tuebingen. dẽ Electronic address: michael. ding felder uni-tuebingen. de dominance at a backward angle can be drawn by assuming a purely spin-fiip transition [4]. The transverse electric field of the incoming electron is negligibly small in this particular case if the excitation energy E is small in comparison with the transferred momentum q, i.e. , E &&qfi, c. The same result...

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Section: Motivationsupporting

confidence: 67%

“…The total angular momentum J(m, t) [Eq. (14)] is symmetrized over the signature m =~1 ; see Appendix B. The isoscalar coupling constant kp of HF" is determined microscopically [36] in order to restore the rotational invariance of the model Hamiltonian, violated by the deformation.…”

Section: Transition Densities In the Qrpamentioning

confidence: 99%

Competing electric and magnetic excitations in backward electron scattering from heavy deformed nuclei

1995

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“…The coefficients b ν (XL) are given, e.g., in Ref. [35]. The quantities R tr are weighted moments of the transition charge density and the transition current density (see, e.g., [36]).…”

Section: Discussionmentioning

confidence: 99%

“…From the seven spectra, a consistent set of 18 peaks which could be identified in most spectra was selected for further analysis. A model-independent analysis (see, e.g., [35]) was used in order to establish the multipolarity of the observed transitions and an initial determination of the transition strength. In the plane wave Born approximation (PWBA), the reduced transition strength for longitudinal electric transitions (C) or transverse magnetic transitions (M), of multipolarity L, may be written as a power series in the momentum transfer q…”

Section: Discussionmentioning

confidence: 99%

Low-energy magnetic dipole response in 56Fe from high-resolution electron scattering

et al. 2003

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The 56 Fe(e, e ) reaction has been studied for excitation energies up to about 8 MeV and momentum transfers q 0.4-0.55 fm −1 at the Darmstadt electron linear accelerator (DALINAC) with kinematics emphasizing M1 transitions. Additional data have been taken for q 0.8-1.7 fm −1 at the electron accelerator NIKHEF, Amsterdam. A PWBA analysis allows spin and parity determination of the excited states. For M1 excitations, transition strengths are derived with a DWBA analysis using shell-model form factors. The resulting B(M1) strength distribution is compared to shell-model calculations employing different effective interactions. The form factor of the prominent low-lying M1 transition at 3.449 MeV demonstrates its dominant orbital nature. It represents a major part of the scissors mode in 56 Fe.

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“…Furthermore, it is well known that the major strength of the orbital and spin M 1 responses are energetically well separated in the nucleus. In pf -shell nuclei, which are of interest for supernova neutrino-nucleus scattering, the orbital strength is located at excitation energies E x 2-4 MeV [30], while the spin M 1 strength is concentrated between 7 and 11 MeV. A separation of spin and orbital pieces is further facilitated by the fact that the orbital part is strongly related to nuclear deformation [31].…”

Section: Neutrino-nucleus Inelastic Processesmentioning

confidence: 99%

Weak Interaction processes in core-collapse supernova

Martı́nez-Pinedo

2008

Nuclear Physics A

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Electroexcitation of magnetic dipole and other modes in46Ti and48Ti

Cited by 13 publications

References 54 publications

Competing electric and magnetic excitations in backward electron scattering from heavy deformed nuclei

Competing electric and magnetic excitations in backward electron scattering from heavy deformed nuclei

Low-energy magnetic dipole response in 56Fe from high-resolution electron scattering

Weak Interaction processes in core-collapse supernova

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