Shape factor analysis of beta transitions in Pm-149

Shape factor analysis of the beta transitions in¹⁴⁹Pm is carried out for the first time, employing an intermediate image beta ray spectrometer. The ambigous situation arising from the disagreement between reported values in end point energies and intensities of the beta transitions is clarified. An attempt was made to evaluate the NME, for the 780 keV beta transition, using Simms formalism.     

States inN=80140Nd populated in the decay of140Pm

The level structure of theN=80,¹⁴⁰Nd has been investigated through the beta decay of^140m Pm and^140g Pm, whose decay half-lives were measured to be 5.95±0.05 min and 9.1±0.5 sec, respectively. Decay schemes for the two isomers have been constructed fromγ-ray measurements. With the help of the beta decayft values and internal conversion electron measurements, spins and parities were deduced for levels in¹⁴⁰Nd. Among the levels a 7^? state at 2222.0 keV and a 5^? state at 2273.3 keV are identified as two-neutron quasiparticle states. The (ie233-01) for^140m Pm and^140g Pm have been deduced as 7^? and 1⁺, respectively. From beta end-point measurements, the decay energies of the two isomers have been determined asQ _EC=6.48±0.07 MeV^140m (Pm) andQ _EC=6.08±0.10 MeV (^140gPm). The results are discussed in the light of nuclear systematics of theN=79 and 80 isotones.     

Kernspektroskopische Untersuchungen am Zerfall des115m Cd

The energy levels in¹¹⁵In at 934, 1133, 1291, and 1419 keV weakly populated by β^?-decay from^115m Cd have been studied by angular correlation measurements using NaJ(Tl)-detectors. The previously measured angular correlations of the (485–934) keV cascade—which is practically isotropic—and the (158–1133) keV cascade were remeasured with higher accuracy. A 286 keV transition between the 1419 and the 1133 keV energy levels was observed and the highly anisotropic angular correlation of the (286–1133) keV cascade was also measured.     

Decay of oriented149Nd and levels in theN=88149Pm nucleus

Levels in the¹⁴⁹Pm nucleus populated via¹⁴⁹Nd decay were studied using the low temperature nuclear orientation technique. The parent¹⁴⁹Nd nuclei were oriented in a gadolinium host. The normalized gamma-ray intensities were determined for twenty five transitions in the daughter¹⁴⁹Pm nucleus. The spins of the¹⁴⁹Pm levels at 288.2 and 425.3 keV were determined as 9/2 and 7/2, respectively, and for several other¹⁴⁹Pm levels the previous spin-assignments could be unambiguously confirmed. Substantial new information on multipole mixing ratios of gamma-transitions in¹⁴⁹Pm is presented. Low-energy level spacing in the¹⁴⁹Pm nucleus is found to be in reasonable agreement with recent particle-rotor model calculations including the variable moment of inertia.     

Decay of149Gd and directional correlations of gamma cascades in149Eu

The decay of¹⁴⁹Gd(9.4d) to the levels of¹⁴⁹Eu has been studied using large volume high resolution Ge(Li) and NaI(Tl) detectors,γ-γ coincidence and directional correlation experiments have been performed. Newγ-rays at energies 131.9, 278.6, 384.7, 415.7, 599.2, 726.5, 734.7, 956.4 and 1,231.1 keV in¹⁴⁹Eu have been observed. Three new levels in¹⁴⁹Eu have been placed at 956.4, 1,082.0 and 1,231.1 keV. Spin-parity assignments have been made to some of the levels in¹⁴⁹Eu. Multipolarity assignments have been made for most of the electromagnetic transitions from the conversion coefficients obtained through the knowledge of ourγ-transition intensities and the published conversion-electron intensities. Based on the newγ-transitions observed in the singles and coincidence spectra, a revised level scheme has been proposed for¹⁴⁹Eu and compared with previously published level schemes. Radioactivity¹⁴⁹Gd; measuredT _1/2,T _γ,γγ coin, γγ(θ), I.C.C.,¹⁴⁹Eu deduced levels,J,γ-mixing,π. Enriched targets, Ge(Li) detectors.     

The decay of143Sm to levels in143Pm

The beta decay of¹⁴³Sm was reinvestigated with the aid of a Ge(Li) detector. Levels of¹⁴³Pm at 271.8, 1,056.5, 1,173.4, 1,342.1, 1,403.2, 1,514.9, 1,752.8, 1,816.3, 1,853.6, (2,000), 2,009.0, 2,080.5, 2,344, 2,443, 2,463, 2,906 and (3,054) keV were established. Logft values for all observed beta transitions have been calculated. Spin and parity assignments have been made from electron capture and positon disintegration considerations and gamma branches. The experimental level scheme of¹⁴³Pm is compared with the results of 1 and 3 q.p. calculations forN=82 nuclei.     

Radioactive decay of 1.7-h149Nd to levels of transitional149Pm

Sources of¹⁴⁹Nd were produced by thermal-neutron irradiation of enriched¹⁴⁸Nd. High resolution Ge(Li) spectrometers were used to collect gamma-ray singles and coincidence spectra in the study of the decay of 1.7-h¹⁴⁹Nd. A total of 214 gamma rays have been assigned to the decay of¹⁴⁹Nd, and 201 of these transitions have been placed in a level scheme of¹⁴⁹Pm involving 42 excited states. Absolute values for the beta-group intensities were determined for transitions to the¹⁴⁹Pm levels, and spin and parity assignments were made for many of the observed states. The experimentally determined level structure of¹⁴⁹Pm was compared with corresponding levels in other odd-mass Pm and Eu nuclides. Interpretations were made in terms of the core-coupling model. Radioactive decay¹⁴⁸Nd(n, γ)¹⁴⁹Nd; measuredE _γ,I _γ,γ-γ coinc.¹⁴⁹Pm deduced levels,J,π. Compton-suppression. Ge(Li) detector. Enriched targets.     

High resolutionL- andM-subshell internal conversion studies of low energy transitions in149Sm and151Eu

The internal conversion subshell intensities of the (21.529±0.014) keV transition in¹⁵¹Eu and the (22.494±0.011) keV transition in¹⁴⁹Sm have been determined in a high resolution investigation using a double-focussing iron-core spectrometer. The subshell ratios yielded unambiguousM1+E2 multipole mixtures for both transitions. δ²(E2/M1) for the 21.53 keV transition was determined to be (8.8±0.7)·10^?4 and for the 22.49 keV transition to be (5.5±1.2)·10^?3.     

The 1-(1.9 MeV β-)2+ transition in the decay of148Pm

The non-unique first-forbidden 1^?(1.9 MeVβ ^?)2⁺ transition in the decay of¹⁴⁸Pm is studied. The nuclear matrix elements are evaluated using for the ground state of the odd-odd¹⁴⁸Pm a phenomenological wave function derived in a previous work in the framework of the two-quasiparticle model and assuming that the first excited 2⁺ state in¹⁴⁸Sm can be described as the first quadrupole phonon state. This model provides nuclear matrix elements which are capable of describing experimental data like the spectrum shape factor, the longitudinal polarization of the electrons and a particular set ofβ-γ directional correlation coefficients, but it fails to interpret the large logft value of this transition. In addition, the validity of theξ-approximation is discussed.     

Decay of194Os andL 1 subshell yields atZ=77

The relative intensities of x rays and gammas emitted in the beta decay of¹⁹⁴Os are measured. No evidence for the feeding of a level at 83 keV in¹⁹⁴Ir is found. An upper limit of 1.7×10^?4 was set for theK shell internal ionization probability in the beta decay to the ground state of¹⁹⁴Ir. TheL-conversion coefficient of 43 keV transition is found to be 12.1 and the transition is mainly ofM1 type with an admixture of 1.3%E2 type. TheL ₁ subshell yields atZ=77 are determined to beω ₁=0.16±0.04,f ₁₂=0.11±0.04 andf ₁₃=0.37±0.03.     

Structure of140Pm from beta decay of140Sm

The structure of¹⁴⁰Pm is investigated through the beta decay of¹⁴⁰Sm, whose half-life is measured to be (14.7 ± 0.2) m. A level structure comprising 41 transitions among 17 excited states is constructed. Using the deduced ft values and measured internal conversion coefficients, spin-parity assignments to several states in¹⁴⁰Pm were made. From beta end-point measurement, the total decay energy is deduced to beQ _EC =3.4±0.3 MeV, which is compared with the predictions of several mass formulae. The systematics of the odd-Z, N=79 isotones are discussed.     

Messung des Elektroneneinfangs am Kern176m Lu

The electron capture of^176m Lu to the ground state and to the first excited state of¹⁷⁶Yb has been observed by measuring the YbK x-rays and the 82,2 keV gamma-rays from the gamma decay of the first excited state in¹⁷⁶Yb. With the data of the 88,36 keV gammarays following the beta decay of^176m Lu to the first excited state of¹⁷⁶Hf the electron capture/beta decay ratio of^176m Lu was found to be (0,95±0,16)·10^?4. The electron capture branching ratio to the ground state and to the first excited state of¹⁷⁶Yb was found to be 40/60±30%. By analyzing the 88,36keV gamma-rays and the HfKx-rays the halflife of^176m Lu was evaluated to be 3,66±0,04 h. The value for theK-conversion coefficient of the 88,36keV transition was determined from the x-ray/gamma-ray ratio to be 1,19±0,09.     

Lebensdauer- und Spinrotationsmessungen an den ersten angeregten Zuständen in197Pt und197Hg

The magnetic moment of the 134 keV state of¹⁹⁷Hg was measured by the differential angular correlation method. The half life of the state was redetermined and the half life of the 53 keV state in¹⁹⁷Pt was determined. The results are:μ(134 keV state in¹⁹⁷Hg)=+0.950(65) nmT _1/2(134 keV state in¹⁹⁷Hg)=7.3(2) nsT _1/2(53 keV state in¹⁹⁷Pt)=16.5(1.5) ns.     

Study of the excited states of119Sn by the decay of119g+m In

The decay of^119g+m In to the excited states of¹¹⁹Sn was investigated.¹¹⁹In was produced by the¹²⁰Sn(γ,p)¹¹⁹In reaction on an enriched SnO₂ target. The isomeric transition of 311.25 keV to the¹¹⁹In ground state was observed. In the beta decay of^119m In excited states at 23.9, 920.5, 921.4, 1089.0, 1187.9 and 1249.6keV in¹¹⁹Sn withJ ^π values of 3/2⁺, 3/2⁺, 5/2⁺, 5/2⁺, 3/2⁺ and 1/2⁺ respectively, are fed. In the decay of the¹¹⁹In ground state only the 7/2⁺ level in¹¹⁹Sn at 787.0 keV is fed.     

Beta-Gamma-Winkelkorrelation bei146Pm

A measurement of theβ-γ directional correlationω(W, Θ) of the 3^?(β)2⁺(γ)0⁺ decay of¹⁴⁶Pm is described. Spin and parity of the ground state of¹⁴⁶Pm are found to be 3^?. A set of matrix elementsY=0.94;x=0.20;u=0.20;z=1, which is chosen to fit the experimental results for ω(W, Θ) and which is in agreement with the CVC theory, indicates aK-selection rule effect for the 0,795 MeV beta transition of¹⁴⁶Pm.     

Decay of the 4.2-min152Pm into levels of152Sm

After bombardments of enriched¹⁵²Sm with 14-MeV neutrons, three isomers of¹²⁵Pm reaction, have been observed with half-lives of 4.2±0.2 min, 7.5±0.2 min and 15.0±1.0 min. Sources of pure 4.2-min¹⁵²Pm were obtained by separating the promethium from its parent 11-min¹⁵²Nd produced by thermal-neutron induced fission of²³⁵U. The beta and gamma radiations of the 4.2-min¹⁵²Pm have been investigated using semiconductor and scintillation spectrometers. Most of theγ-ray transitions could be placed in a level scheme for 152Sm. Especially interesting is a level at 1083 keV for which the assignmentI ^π=0⁺ is proposed. In a 4πβγ experiment, the ground state feeding of¹⁵²Sm in theβ ^?-decay of the 4.2-min¹⁵²Pm has been measured to be 61% of allβ-ray transitions. AQ _β-value of 3.4±0.2 MeV has been obtained.     

Conversion electron measurements in the decay of156Tb

The conversion electron spectrum from the decay of¹⁵⁶Tb to¹⁵⁶Gd was measured with an iron, double-focusing spectrometer. TheK conversion coefficient of the 1222.4 keV transition was measured relative to theK conversion coefficient of the 661.6 keV transition in¹³⁷Cs and found to be 0.00174±0.00013. This result was used to normalize electron and gamma-ray data to obtain theK conversion coefficients of 33 transitions in¹⁵⁶Gd. The 1009.6 and 1040.6 keV transitions have largeE0 components.     

First evidence for the 2+ level in the very neutron-rich nucleus102Sr

Evidence for the 2⁺ level in¹⁰²Sr is obtained from theβ-decay of¹⁰²Rb, mass separated at the ISOLDE facility. The energy of 126 keV and the collectivity of the 2⁺→0⁺ transition indicate that¹⁰²Sr is a strongly deformed rigid rotor. In addition, a sizeable lifetime is measured for the 94 keV transition in¹⁰²Y.     

The decay of121g+m In to levels in121Sn

The decay of¹²¹ g+m In to the excited states of¹²¹Sn was investigated.¹²¹In was produced by the¹²²Sn(γ,p)¹²¹In reaction on an enriched SnO₂ target. Strong indications of the isomeric transition of 321 keV to the¹²¹In ground state were found. In the beta decay of^121m In excited states at 60.1, 908.9, 1101.9, 1120.4, 1403.0, 2864.1, 3119.8 and 3228 keV in¹²¹Sn withJ ^π values 1/2⁺, 3/2(5/2)⁺, 3/2⁺, 5/2⁺, 5/2⁺ and 1/2⁺ or 3/2⁺ for the three levels around 3 MeV, are fed. In the decay of the¹²¹In ground state only the 7/2⁺ level in¹²¹Sn at 925.3 keV is fed.