Search

The method of relative self absorption is based on the technique of nuclear resonance fluorescence measurements. It allows for a model-independent determination of ground-state transition widths, natural level widths, and, consequently, of branching ratios to the ground state for individual excitations. Relative self–absorption experiments have been performed on the nuclei 6Li and 140Ce. In order to investigate the total level width for the 0+1, T = 1 level at 3563 keV in 6Li, a high-precision self-absorption measurement has been performed. In the case of 140Ce, self absorption has been applied for the first time to study decay widths of dipole-excited states in the energy regime of the pygmy dipole resonance.

The electric dipole strength distribution in 48Ca between 5 and 25 MeV has been determined at RCNP, Osaka from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the first extraction of the electric dipole polarizability αD(48Ca)=2.07(22) fm³. Remarkably, the dipole response of 48Ca is found to be very similar to that of 40Ca, consistent with a small neutron skin in 48Ca. The experimental results are in good agreement with ab initio calculations based on chiral effective field theory interactions and with state-of-the-art density-functional calculations, implying a neutron skin in 48Ca of 0.14-0.20 fm. [ABSTRACT FROM AUTHOR]

Background: The quenching of spin-isospin modes in nuclei is an important field of research in nuclear structure. It has an impact on astrophysical reaction rates and on fundamental processes like neutrinoless double- ß decay. Gamow-Teller (GT) and spin-flip M1 strengths are quenched. Concerning the latter, the Jp = 1+ resonance in the doubly magic nucleus 48Ca, dominated by a single transition, serves as a reference case. Purpose: The aim of the present work is to search for weak M1 transitions in 48Ca with a high-resolution (p, p') experiment at 295 MeV and forward angles including 0° and a comparison with results from a similar study using backward-angle electron scattering at low momentum transfers in order to estimate their contribution to the total B (M1) strength in 48Ca. Methods: The spin- M1 cross sections of individual peaks in the spectra are deduced with a multipole decomposition analysis (MDA) and converted to reduced spin- M1 transition strengths by using the unit cross-section method. For a comparison with electron-scattering results, corresponding reduced B (M1) transition strengths are extracted following the approach outlined in Birkhan et al. [Phys. Rev. C 93, 041302(R) (2016)]. Results: In total, 30 peaks containing a M1 contribution are found in the excitation energy region 7-13 MeV. The resulting B (M1) strength distribution compares well to the electron-scattering results considering different factors limiting the sensitivity in both experiments and the enhanced importance of mechanisms breaking the proportionality of nuclear cross sections and electromagnetic matrix elements for weak transitions as studied here. The total strength of 1.14(7) µ²N deduced assuming a nonquenched isoscalar part of the (p, p') cross sections agrees with the (e, e') result of 1.21(13) µ²N. A bin-wise analysis above 10 MeV provides an upper limit of 1.51(17) µ²N. Conclusions: The present results confirm the previous electron-scattering work that weak transitions contribute about 25% to the total B (M1) strength in 48Ca and the quenching factors of GT and spin- M1 strength are then comparable in f p -shell nuclei. Thus, the role of meson-exchange currents seems to be negligible in 48Ca, in contrast to sd -shell nuclei. [ABSTRACT FROM AUTHOR]

Inelastic proton scattering at energies of a few hundred million electron volts and extreme forward angles selectively excite the isovector spin-flip M1 (IVSM1) resonance. A method based on isospin symmetry is presented to extract its electromagnetic transition strength from the (p,p') cross sections. It is applied to 48Ca, a key case for an interpretation of the quenching phenomenon of the spin-isospin response, and leads to a M1 strength consistent with an older (e,e') experiment excluding the almost two times larger value from a recent (γ,n) experiment. Good agreement with electromagnetic probes is observed in 208Pb, suggesting the possibility of extracting systematic information on the IVSM1 resonance in heavy nuclei. [ABSTRACT FROM AUTHOR]

Background: The B(E2) transition strength to the 22+ state in 94Zr was initially reported to be larger by a factor of 1.63 than the one to the 2+ state from lifetime measurements with the Doppler-shift attenuation method using the (n,n'y) reaction [Elhami et al., Phys. Rev. C 75, 011301(R) (2007)]. This surprising behavior was recently revised in a new measurement by the same group using the same experimental technique leading to a ratio below unity as expected in vibrational nuclei. Purpose: The goal is an independent determination of the ratio of B(E2) strengths for the transitions to the 21,2+ states of 94Zr with inelastic electron scattering. Method: The relative population of the 21,2+ states in the (e,e') reaction was measured at the S-DALINAC in a momentum transfer range q = 0.17-0.51 fm-1 and analyzed in plane-wave Born approximation with the method described by Scheikh Obeid et al. [Phys. Rev. C 87, 014337 (2013)]. Results: The extracted B(E2) strength ratio of 0.789(43) between the excitation of the 21+ and 22+ states of 94Zr is consistent with but more precise than the latest (n,n'y) experiment. Using the B(E2) transition strength to the first excited state from the literature a value of 3.9(9) Weisskopf units is deduced for the B(E2; 22+➔01+)transition. Conclusions: The electron scattering result independently confirms the latest interpretation of the different (n,n'y) results for the transition to the 22+ state in 94Zr. [ABSTRACT FROM AUTHOR]

A direct measurement of the decay width of the excited 0+1 state of 6Li using the relative self-absorption technique is reported. Our value of Γγ,0+1→1+1=8.17(14)stat.(11)syst. eV provides sufficiently low experimental uncertainties to test modern theories of nuclear forces. The corresponding transition rate is compared to the results of ab initio calculations based on chiral effective field theory that take into account contributions to the magnetic dipole operator beyond leading order. This enables a precision test of the impact of two-body currents that enter at next-to-leading order. [ABSTRACT FROM AUTHOR]

The E2/M1 multipole mixing ratio δ1→2 of the 1sc+→21+ γ-ray decay in 156Gd and hence the isovector E2 transition rate of the scissors mode of a well-deformed rotational nucleus has been measured for the first time. It has been obtained from the angular distribution of an artificial quasimonochromatic linearly polarized γ-ray beam of energy 3.07(6) MeV scattered inelastically off an isotopically highly enriched 156Gd target. The data yield first direct support for the deformation dependence of effective proton and neutron quadrupole boson charges in the framework of algebraic nuclear models. First evidence for a low-lying Jπ=2+ member of the rotational band of states on top of the 1+ band head is obtained, too, indicating a significant signature splitting in the K=1 scissors mode rotational band. [ABSTRACT FROM AUTHOR]

A direct measurement of the decay width of the excited 0_{1}^{+} state of ^{6}Li using the relative self-absorption technique is reported. Our value of Γ_{γ,0_{1}^{+}→1_{1}^{+}}=8.17(14)_{stat.}(11)_{syst.}  eV provides sufficiently low experimental uncertainties to test modern theories of nuclear forces. The corresponding transition rate is compared to the results of ab initio calculations based on chiral effective field theory that take into account contributions to the magnetic dipole operator beyond leading order. This enables a precision test of the impact of two-body currents that enter at next-to-leading order.

The electric dipole strength distribution in ^{48}Ca between 5 and 25 MeV has been determined at RCNP, Osaka from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the first extraction of the electric dipole polarizability α_{D}(^{48}Ca)=2.07(22)  fm^{3}. Remarkably, the dipole response of ^{48}Ca is found to be very similar to that of ^{40}Ca, consistent with a small neutron skin in ^{48}Ca. The experimental results are in good agreement with ab initio calculations based on chiral effective field theory interactions and with state-of-the-art density-functional calculations, implying a neutron skin in ^{48}Ca of 0.14-0.20 fm.

The E2/M1 multipole mixing ratio δ_{1→2} of the 1_{sc}^{+}→2_{1}^{+} γ-ray decay in ^{156}Gd and hence the isovector E2 transition rate of the scissors mode of a well-deformed rotational nucleus has been measured for the first time. It has been obtained from the angular distribution of an artificial quasimonochromatic linearly polarized γ-ray beam of energy 3.07(6) MeV scattered inelastically off an isotopically highly enriched ^{156}Gd target. The data yield first direct support for the deformation dependence of effective proton and neutron quadrupole boson charges in the framework of algebraic nuclear models. First evidence for a low-lying J^{π}=2^{+} member of the rotational band of states on top of the 1^{+} band head is obtained, too, indicating a significant signature splitting in the K=1 scissors mode rotational band.

A new technique for immediate though temporary relief of airway obstruction due to tracheal stenosis is described. Introduction of a small gauge cuffed endotracheal tube past the stenotic segment, followed by repeated withdrawal with the cuff inflated, allows for effective and safe retrograde bougienage. Airway patency is maintained throughout. Following this procedure introduction of an endotracheal tube or tracheostomy cannula is facilitated and definitive surgery can be planned.

We compared the action of alfentanil on experimental myocardial infarction size with two widely used anesthetic drugs: fentanyl and halothane. Myocardial infarction size, measured by histological techniques, was identical for the three drugs investigated. Our results demonstrate that the action of alfentanil on factors governing myocardial oxygen supply and demand in the rat with coronary artery ligation is no different from the action of fentanyl or halothane.