Energy levels of Kr populated by Br decay

The γ-rays following the β-decay of ⁸²Br have been investigated using a 220 mm³ Ge(Li) detector, an anti-Compton NaI(Tl) spectrometer and a two-dimensional coincidence arrangement. The ⁸²Br was produced by thermal neutron activation of ammonium bromide. The presence of eight, well-known and 11 weak γ-rays has been established. It has been shown through half-life measurements that the newly identified γ-rays belong to ⁸²Br decay and that the high-energy peaks are not to summing effects. All the reported transitions have been incorporated in a level scheme of ⁸²Kr by introducing levels at 0, 776, 1474, 1820, 1953, 2093, 2426, 2554, 2647 and 2828 keV. Limits on probable spin and parity values for the newly-introduced levels have been established. The level introduced at 2828 keV on the basis of a 1008–1043 keV γγ-coincidence must be fed by a weak β-branch of ⁸²Br with an end-point energy of 263 keV and log ft of approximately 6.1.     

The decay of 23.0 min Rb to levels in Kr

The radioactive decay of ⁷⁹Rb(23.0±0.5 min) has been studied with the aid of semiconductor radiation detectors. Both singles and coincidence spectra have been recorded. The decay energy: 3520±45 keV was determined by measuring the endpoint of the positon spectrum in coincidence with prominent γ-rays. A decay scheme is proposed incorporating most of the measured γ-rays. The following energies in keV and parities of levels are assigned: ground state ( ), , , , , 383.71±0.18, 532.82±0.33, 688.21±0.09, , 934.0±1.4, 1089.4±0.4, 1474.7±0.3. The spin and parity of the ⁷⁹Rb ground state is most probably .     

Prompt γ-rays from Pb following neutron emission from muonic Pb

We have measured the energies and intensities of prompt γ-rays from ²⁰⁶Pb that follow neutron emission from muonic ²⁰⁷Pb. For the levels at 803, 1704 and 2648 keV we deduce muonic isomer shifts. By comparing the relative and absolute yields of the γ-rays with the intensities of neutron groups observed in (γ, n) reactions, we find that roughly 50% of the prompt neutrons from muonic ²⁰⁷Pb result from radiationless deexcitation of atomic levels with .     

The decay of 91 min As

The energies and relative intensities of γ-rays following the β-decay of ⁷⁸As (and ⁷⁶As) to levels in ⁷⁸Se (and ⁷⁶Se) have been measured using an 8 cm³ Ge(Li) spectrometer. The β-decay of ⁷⁸As has been measured using a superconducting magnet beta-ray spectrometer with two 3 mm thick Si(Li) detectors. These data plus β-γ and γ-γ coincidence results have been used to construct a level scheme with 18 excited levels in ⁷⁸Se. The half-life of ⁷⁸As was measured to be 90.7±0.2 min.     

Spin-dependent reaction mechanism in Ti(d, p)Ti from proton-γ correlation

The γ-decays of the states in ⁴⁷Ti at 157 keV and 1547 keV have been studied following the ⁴⁶Ti(d, p)⁴⁷Ti reaction at 5.0 MeV incident energy. Protons were detected at 0° with a semiconductor detector. The angular correlations of the γ-rays with the reaction protons were measured. The E2/M1 mixing ratios of the γ-decays and the population ratios of the to the substates were deduced. From the non-zero population of the substate it was concluded that a spin-flip mechanism exists in the ⁴⁶Ti(d, p)⁴⁷Ti stripping reaction.     

Low-intensity transitions in the decay of Rb

The γ-rays following the decay of ⁸⁸Rb have been studied with a 40 cm³ Ge(Li) detector with the aim of resolving discrepancies in some recent determinations of the decay scheme of this isotope. The existence of a 1799 keV γ-ray has been confirmed and three new γ-rays with energies of 1218, 1295 and 1368 keV have been found. All of these results are in good agreement with a decay scheme recently proposed by Ragaini and Knight.     

Decay of Ru, Zr and Nb

The decay of ⁹⁷Ru, ⁹⁷zr and ⁹⁷Nb to levels in ⁹⁷Tc, ⁹⁷Nb and ⁹⁷Mo has been studied with Ge(Li), NaI(Tl), plastic scintillation, and Si (Li) detectors in singles and coincidence experiments. Level schemes were constructed with states in ⁹⁷Te at 96.5, 215.2, 324.4, (560), 785.5, 856 and 971 keV; in ⁹⁷Nb at 743.5, 1148.6, 1251.4, 1276.6, 1549.2, 1751.2, 1764.0, 1852.0, 2106.9 and 2247 keV; and in ⁹⁷Mo at 656.0, 1022.0, 1274.5 and 1514 keV. From β-endpoint energies, disintegration energies of ⁹⁷Zr and ⁹⁷Nb were determined to be 2580 ± 50 keV and 1830 ± 50 keV, respectively. Decay scheme considerations and an upper limit to the β⁺/ec ratio established the disintegration energy of ⁹⁷Ru to be about 1100 keV. Neither the effective-interaction method nor the pairing-correlation model accounts for the experimentally determined levels in mass-97 nuclei.     

Decay of the 55 min and 12 min Te isomers

Gamma rays emitted in the decay of the ¹³³Te isomers, 55.4 min ^133mTe and 12.5 min ^133gTe, have been observed with Ge(Li) detectors. Sources were prepared by separating Sb from fission products, allowing several minutes for decay of 2.7 min ¹³³Sb and then separating the Te daughter activities. A total of 29 γ-rays between 312 and 2541 keV were attributed to decay of ^133gTe and 30 from 74 to 2050 keV to that of ^133mTe. Gamma-gamma coincidences in the decay of ^133gTe were observed with a NaI(Tl)---Ge(Li) set-up. The decay scheme of ^133gTe was constructed, involving placement of 25 of the γ-rays emitted. The decay of ^133gTe populates levels in ¹³³I at 0, 312, 720, 787, 1313, 1333, 1374, 1565, 1718, 2137, 2194 and 2541 keV. The decay of ^133mTe is very complicated, and we have not attempted construction of a complete decay scheme for it; however, levels at 913 and 1561 keV in ¹³³I are definitely populated in ^133mTe decay. The value for Q_β of ¹³³Te was measured as 3.52±0.10 MeV. The low-lying levels of the odd-mass iodine isotopes vary smoothly through the series ¹²⁵I through ¹³³I. The levels of ¹³³I are fitted rather well by predictions based on quasi-particle-phonon coupling.     

Rotational excitations in residual nuclei produced by stopped negative pions on targets of Ho, Lu, Lu, Hf, and Ta

Reactions produced by stopped negative pions on targets of ¹⁶⁵Ho, ¹⁷⁵Lu, ¹⁷⁶Lu, ¹⁷⁹Hf, and ¹⁸¹Ta are investigated by measuring photons coincident with the stopped pions. These photons were detected with an 80 cm³ Ge(Li) detector and identified as pionic X-rays or rotational γ-rays from the residual nuclei. Pion capture is found to result in the excitation of high-spin states. Yields for the residual nuclei are inferred from the observed γ-transitions and compared to calculations based on the exciton model for pre-equilibrium emission followed by particle evaporation. Preliminary results of a pion stop, γn coincidence experiment are presented and compared to the calculations.     

The decay scheme of Ag

The γ-radiations following the decay of ¹¹²Ag have been studied with Ge(Li) detectors. The ¹¹²Ag half-life has been measured as 3.16±0.02 h; twenty gamma radiations ranging in energy from 606.7 keV to 2829.6 keV have been observed.

Gamma-gamma coincidence measurements have been performed with Ge(Li) and NaI(Tl) detectors. A decay scheme consistent with the present data is proposed.     

The decay of 1.2 min Ag and 5.3 h Ag

The decay schemes of 1.2 min and 5.3 h ¹¹³Ag have been studied using Ge(Li) and NaI(Tl) detectors and a 4096-channel multiparameter pulse-height analyser system. The decay of 5.3 h ¹¹³Ag was found to involve 15 γ-rays and to produce 10 excited states in ¹¹³Cd at energies of 264.7, 298.0, 315.6, 583.9, 604.6, 681.1, 883.6, 936.9, 989.0 and 1195.2 keV. The italicized energies refer to negative parity states, through which 1.3% of the decays go to yield the isomer at 264.7 keV. The 604.6 keV level is thought to be a case|9/2⁻ level similar for those found in several odd-mass Te and Xe isotopes. The 1.2 min ^113mAg decay was found to populate several of the same levels in Cd and two additional levels at 452 and 689 keV. The 1.2 min ¹¹³Ag is the upper isomer with high spin, probably .     

Collective properties of Cr

The mean lifetimes of levels below 3 MeV excitation in ⁴⁹Cr were measured using the reaction ⁴⁹Ti(, nγ)⁴⁹Cr. The Doppler-shift attenuation method was used in a neutron-gamma coincidence measurement. The lifetime of the first excited state was determined with the recoil distance method. The results are : 272 keV, 19±5 ps; 1085 keV, 260±90 fs; 1563 keV, 590₋₁₂₀⁺³⁰⁰ fs; 1704 keV, > 5.5 ps; 1742 keV, > 4 ps; 1982 keV, > 6.5 ps; 2169 keV, > 4.5 ps; 2433 keV, > 6 ps; 2504 keV, < 12 fs; 2614 keV, 65 ±20 fs. The lifetimes of the second and third excited states in combination with known multipole mixing ratios gave evidence for spin assignments of for the 1085 keV level and for the 1563 keV level. The energies and spins of the four lowest levels as well as the B(M1) and B(E2) values of their γ-decays are in good agreement with calculations based on the strong coupling model and suggest that these levels are strongly collective. Dipole transitions of the higher levels to the ground and first excited states are highly retarded.     

The energy levels of Al

The energies and strengths of ²⁵Mg(p, γ), ²⁵Mg(p, p₁) and ²⁵Mg(p, p₂) resonances were determined in the energy range E_p < 2 MeV. Four new (p, γ) resonances were observed at E_p = 736.2±0.7, 818.1±0.7, 834.6±0.7 and 1514.7±0.7 keV. The γ-decay of 44 resonances and 49 bound levels was established. The energies of 41 and mean lifetimes of 25 bound levels were determined. Two new levels at E_x = 4952.4±1.4 keV and 5141.7±2.0 keV were observed. Angular distributions yielded unique spins for five resonance levels. Weisskopf estimates allowed unique spin assignments for five resonances. The Q-value of the ²⁵Mg (p, γ) ²⁶Al reaction was found to be 6305.0±1.2 keV.     

The decay of Cs

In a study of the level scheme of ¹³¹Cs, we have measured the γ-γ and the ce-γ directional correlations of the 496-123.7 keV and 486-133.5 keV cascades. The linear polarization at φ=90° was measured for the 496-123.7 keV and 486-133.5 keV cascades. The L-subshell ratios for the 123.7 keV transition were determined. The g-factor of the 133.5 keV level and the half-lives of the 78.7, 123.7, 133.5 and 216 keV levels were re-investigated. The spin and parity assignments derived for the 620, 133.5 and 123.7 keV levels are , respectively. The 620, 496, 486, 133.5 and 123.7 keV transitions are found to be of pure E2, pure M1, pure E2, (M1+(22±2)%E2) and pure E2 multipolarity, respectively. An upper limit of 192 ps for the half-life of the 216 keV level is obtained. The results are compared with theoretical estimates from the calculations of Kisslinger and Sorensen, of Freed and of Freed and Miles.     

Effect of E1 decay in the population of superdeformed structures

Spectra of the yrast and excited superdeformed bands, forming the E2 quasi-continuum, are measured with the EUROBALL array for the nucleus ¹⁴³Eu, in coincidence with high-energy γ-rays (E_γ>3 MeV). It is found that the intensity population of the superdeformed states is enhanced by a factor of ≈1.6 when a coincidence with a γ-ray with energy >6 MeV is required, in reasonable agreement with the increase of the line shape of the Giant Dipole Resonance built on a superdeformed configuration. This result shows that when an high energy E1 γ-ray is involved in the decay it is more likely connected with a SD rather than a ND nucleus. In addition, the analysis of the rotational quasi-continuum suggests the presence of a superdeformed component. The data are also compared and found consistent with simulation calculations of the relative intensities of the SD states, including the E1 decay of superdeformed nature.     

Polarisation circulaire du rayonnement gamma de Sb, Cs et Ag

The βγ circular polarization correlation of the 3⁻(β⁻ 621 keV)3⁻(γ 1692)2⁺ cascade in ¹²⁴Sb, the 4⁺(β⁻ 662)4⁺ (γ 796)2⁺ (γ 605)0⁺ in ^13Z4Cs and the 6⁺(β⁻529)6⁺ (γ 937)4⁺ (γ 885)2⁺ (γ 658)0⁺ in ^110mAg have been studied by using a Compton effect polarimeter. The measured asymmetry parameters are 0.172±0.004, −0.0702 ±0.0024 and 0.0549±0.0013 respectively.     

The decay of Ho and Ho

The disintegration characteristics of ^164mHo and ^164gHo have been studied using a high-resolution Ge(Li) spectrometer. Radioactive samples of ^164mHo and ^164gHo were obtained through the (n, 2n) reaction on spectroscopically pure holmium oxide with 14 MeV neutrons. The isomeric cross-section ratio for the yields of the ground and metastable states has been estimated to be 1.0±0.25. Gamma rays of 37.7 and 56.1 keV energy have been assigned to the decay of ^164mHo and 73.4 and 91.5 keV γ-rays are attributed to the decay of ^164gHo by electron capture and negaton emission, respectively. The branching ratio for the electron capture decay of ^164gHo to the levels in ¹⁶⁴Dy has been estimated accurately from the analysis of X-ray intensities. The results have been incorporated into a decay scheme.     

The Fermi matrix elements inferred from β-γ(CP) correlation measurements in Fe decay

Measurements have been made of the β-γ circular-polarization correlation paramter A for the 273 keV β-branch in the decay of ⁵⁹Fe. It has recently been established that each of the principal β-branches of ⁵⁹Fe involves ΔJ=0 and thus has a possible non-zero Fermi matrix element M_F which can be determined from the ƒt value and A. Previous β-γ (_CP) measurements on this nucleide have all employed the usual γ-ray scattering technique. This method is suitable for the 475 keV β-branch but does not produce an accurate measurement of the lower energy branch because of energy discrimination difficulties. A transmission polarimeter with γ-discrimination has been used in the present work to obtain clean data on the 273 keV β-1.29 MeV γ-cascade. Calibration with ⁶⁰Co (1.33 MeV) and ²⁸Al (1.79 MeV) yielded A = −0.154±0.023. This gives for the isospin impurity coefficient and the effective Coulomb matrix element of the 1.29 MeV state (1.1±1.4) × 10⁻³ and 9±11 keV, respectively.     

Investigation of parity mixing in Ta and Lu by measurement of the circular polarization of γ-rays

The circular polarization of the 482 keV γ-radiation of ¹⁸¹Ta and the 343 keV γ-radiation of ¹⁷⁵Lu was measured with a Compton polarimeter. Spurious effects arising from higher order contributions of quantum electrodynamics to the Compton scattering cross section were discovered. The results for the polarization are P = − (4.1±1.3)10⁻⁶ for ¹⁸¹Ta and P = − (1.5±6.0)10⁻⁶ for ¹⁷⁵Lu. These values are corrected for instrument asymmetries, bremsstrahlung and intensity of other lines.     

The decay of Sc and V

The decays of ⁴⁸Sc and ⁴⁸V have been studied with Ge(Li) diodes, scintillation spectrometers and a double focussing beta-ray spectrometer. The 3507 keV level, from which originates the quadruple cascade (9.4±0.5)% in the ⁴⁸Sc decay, is also de-excited by a 1212 keV cross-over transition to the 2295 keV (4⁺) level and supports the assumption, that the 3507 keV level has a spin 6⁺. The first member of the reported triple cascade in the ⁴⁸V decay is shown to be a doublet of 928.9±0.7 (1.2±0.2)% and 944.3±0.5 keV (8.0±0.5)% gamma rays, both followed by the 1311.4–983.3 keV cascade. Evidence was found, that the 2421 keV (2⁺) level is excited by weak gamma rays from high-energy levels. The K/β⁺ ration in the ⁴⁸V decay is 0.69±0.05 The Q-values of ⁴⁸Sc and ⁴⁸V are calculated to be 3986±7 keV and if 4015±4 keV, respectively. The energy of the gamma ray of ⁴⁷Sc, which is present as an impurity, is 159.2±0.5 keV.