Untersuchung der γ-Strahlung bei Einfang thermischer Neutronen in Sm149 mit der Summen-Koinzidenzmethode

Two-step cascades of neutron captureγ-rays of Sm¹⁴⁹ (n, γ) Sm¹⁵⁰ have been studied by means of the sum-coincidence method. 11 two-step transitions from the capturing state to the 0,33 and 0.77 MeV states were found. Most of them agree with the decay scheme ofGroshev et al., some are new. The relative intensities of the cascades were determined. No two-step transition from the capturing state to the ground state could be observed. Fig. 3 shows the main result.     

Untersuchung der γ-Strahlung bei Einfang thermischer Neutronen in Nd143 mit der Summen-Koinzidenzmethode

Zeitschrift für Physik A Hadrons and nuclei - 2 two-step cascades from the capturing state to the groundstate of Nd144 and 6 two-step cascades from the capturing state to the 0,69 MeV excited...     

Beugung thermischer Neutronen an einem Strichgitter

The diffraction of thermal neutrons by a plane Ni covered ruled grating was investigated at various angles of incidence. A 54 lines per mm grating was used in the reflection case. The diffraction pattern was observed on both sides of the beam reflected in zero order (total reflection). Measured and calculated intensities are compared.     

Herstellung polarisierter thermischer Neutronen mit Hilfe eines Eisen-Kobalt-Neutronenleiters

A neutron guide is described by means of which a polarized neutron beam is obtained with a polarisation of 80% and a transmission of 60%. The equipment was built up at the 4 MW-research-reactor in Munich and has been used for depolarisation-measurements as well as (n, γ) and (n, β) reactions.     

L II-electron-gamma correlation in199Hg

The(50L _II?158γ) directional correlation has been measured in¹⁹⁹Hg. The result isA ₂₂=+0.038±0.024, which gives the mixing ratio for the 50keV transition,δ=+0.017±0.006. The accuracy of the method is discussed.     

Untersuchung des Niveauschemas von Nb93 durch Messung der Gammastrahlung nach der inelastischen Streuung schneller Neutronen

Fast neutrons from a nanosecond-pulsedD(d, n)He³ neutron source were scattered from Nb⁹³. The gamma spectrum arising from inelastic scattering was measured in a high resolution Ge(Li)-spectrometer. In order to obtain low background a time gate technique was used. About 44 gamma lines could be found between 150 keV and 2.2 MeV in the single spectrum. In addition gamma-gamma-coincidences were investigated with a NaJ- and a Ge(Li)-detector. By these means it was possible to identify almost all gamma transitions and to receive a nearly complete level scheme of Nb⁹³ up to 2.2 MeV. The experimental cross sections for the population of the levels by the (n, n′)-reaction were compared with the results of the Hauser-Feshbach theory using the optical model transmission coefficients of Lindner and Meldner. From this and from the observed gamma transitions proposals for spin- and parity-assignments of the energy levels are given.     

Spinbestimmung der angeregten Zustände verschiedener Kerne aus der Gammazirkularpolarisation nach dem Einfang polarisierter Neutronen

The circular polarisation of the gamma radiation following capture of polarized slow neutrons in natural titanium, chromium, nickel, zinc and selenium was investigated by means of a polarimeter using transmission of magnetized iron as polarization sensitive effect. A large Ge-diode was used for measurement of capture gamma spectra. By this way the spin of 55 levels in Ti⁴⁹, Cr⁵¹, Cr⁵³, Cr⁵⁴, Ni⁵⁹, Ni⁶¹, Ni⁶³, Zn⁶⁵, Zn⁶⁷, Zn⁶⁸, Se⁷⁷ and Se⁷⁸ were determined. In 37 cases existing spin determinations were confirmed, in 1 case our results contradicts earlier spin determinations and 17 new spin assignments were made.     

Electric hyperfine interaction in199Hg fluorides

With the current integration technique, the Mössbauer effect on the 158 keV, 5/2^–1/2^– transition in¹⁹⁹Hg was studied using the cubic HgF₂ and the tetragonal Hg₂F₂ as absorbers; in the latter, a quadrupole splittingeQV _zz=}- 9.0(2) mm/s was observed. Electron densities were calculated with the self-consistent-charge-extended-Hueckel-molecular-orbital method and r ²=(3.26±0.11) fm² derived. From the quadrupole splitting and the calculation, an effective antishielding factor almost twice that of the neutral Hg atom is derived.Dedicated to Professor B. Elschner on the occasion of his 60th birthday.     

Die Konversion des Hg199m

Hg^199m was produced from natural HgO by fastn irradiation. The cascade decay was investigated with scintillation spectrometers by application of the summing technique. The following results were obtained: half-lifeT _1/2=(43±0,5) min; energy of the isomeric transitionE _γ1=(375±3)keV; conversion coefficients α _K375=3,05±0,25; α_total=5,45±0,25; yielding the multipole order of the isomeric transition to beM4+(25±15)%E5; energy of the second transitionE _γ2=(159±2)keV; conversion coefficients α _K159=0,30±0,03; α_total=0,9±0,1, confirming the multipolarityE2 of this transition.     

Hg 199(n,ce) Hg200 studies

The conversion-electron spectrum from slow neutron capture in Hg 199 has been measured with the beta spectrometer at the reactor FRM. Approximately 100 conversion-electron lines with energies between 200 and 2300 keV were observed. The multipolarities and mixing ratios of about 50 transitions were determined. Branching and mixing ratios are compared with theoretical predictions.     

Sub-dekahertz ultraviolet spectroscopy of 199Hg+

Using a laser that is frequency locked to a Fabry-Perot etalon of high finesse and stability, we probe the 5d(10)6s (2)S(1/2)(F = 0)<-->5d(9)6s(2) (2)D(5/2)(F = 2) Deltam(F) = 0 electric-quadrupole transition of a single laser-cooled 199Hg+ ion stored in a cryogenic radio-frequency ion trap. We observe Fourier-transform limited linewidths as narrow as 6.7 Hz at 282 nm ( 1.06x10(15) Hz), yielding a line Q approximately 1.6x10(14). We perform a preliminary measurement of the 5d(9)6s(2) (2)D(5/2) electric-quadrupole shift due to interaction with the static fields of the trap, and discuss the implications for future trapped-ion optical frequency standards.     

Asymmetrie des β-Zerfalls und NMR von28Al,38Cl und116In nach dem Einfang polarisierter Neutronen

Polarized²⁸Al,³⁸Cl and¹¹⁶In nuclei have been produced by capture of polarized thermal neutrons. The nuclear magnetic resonance has been observed by measuring the asymmetry of the β-decay. The nuclear magnetic moments were found to be μ(²⁸Al)=2.789(1) nm and μ(³⁸Cl)=2.05(2) nm (uncorrected). The β-decay asymmetry of¹¹⁶In has been observed in superconducting In-metal.     

Experimental study of 199Hg spin anti-relaxation coatings

We report on a comparison of spin relaxation rates in a ¹⁹⁹Hg magnetometer using different wall coatings. A compact mercury magnetometer was built for this purpose. Glass cells coated with fluorinated materials show longer spin coherence times than if coated with their hydrogenated homologues. The longest spin relaxation time of the mercury vapor was measured with a fluorinated paraffin wall coating.     

199Hg spin-lattice relaxation and chemical shift anisotropy in diphenylmercury

¹⁹⁹Hg spin-lattice relaxation times (T₁) have been measured for diphenylmercury at magnetic fields of 2.35 and 7.05 T. T₁ was nine times shorter at the higher field (0.033 sec at 310 K) than at the lower field (0.30 sec), showing relaxation by chemical shift anisotropy (CSA) to be the dominant mechanism even at the lower field. Variable-temperature ¹³C T₁ measurements at 6.35 T made it possible to determine a value for the correlation time for motion perpendicular to the axis of the molecule (50 psec at 300 K), which with the ¹⁹⁹Hg data allowed a value of 6800 ± 680 ppm to be calculated for the mercury chemical shift anisotropy. The activation energy for rotational motion was 13.3 kJ · mole⁻¹. Previous data on dimethylmercury have been reassessed and the importance of the CSA mechanism for ¹⁹⁹Hg at high fields is pointed out.     

Konversionskoeffizienten und Fluoreszenzausbeuten beim Zerfall des Hg199m

Hg^199m was produced by bombarding natural HgO with fast neutrons. The conversion electrons of the cascade decay were investigated with Si(Li)-counters. By application of the summing technique the conversion coefficients andL-shell fluorescence yields of Hg were determined. The gamma rays were studied with a Ge(Li)-counter. The following results were obtained: half-lifeT _1/2=(42.6± 0.2) min; energies of the transitionsE _γ1=(374.1± 0.1) keV,E _γ1=(158.3± 0.1)keV; intensity ratio of the gamma raysI _γ(158 keV):I _γ(374keV)=(424± 42):100; conversion coefficients α_K158=0.30± 0.03, α_total158=0.94± 0.09, α_K158/α_LM...158=0.47± 0.02, α_L158/α_M...158=3.10± 0.16;α_K374=3.51± 0.28,α_total1374=6.19±0.47,α_K374/α_LM...374=1.32±0.04, α_L374/α_M...374=2.14±0.11;L-shell fluorescence yields \(\bar \omega _L \) =0.40± 0.04, ω_KL=0.41±0.04.