Internal Conversion Coefficient Measurements Research Articles

New Measurements of Internal Conversion Coefficients in $${}^{{111}}$$Cd

New Measurements of Internal Conversion Coefficients in $${}^{{111}}$$Cd

Precision Measurements of Internal Conversion Coefficients of Low Energy Transitions in $${}^{169}$$Tm for Efficiency Calibration of Electron Detectors

The 32.018 d beta decay of $${}^{169}$$ Yb is studied with a high resolution precisely calibrated 8 $$K$$ PC based Multi-Channel Analyzer coupled HPGe gamma spectrometer system and liquid nitrogen cooled Si(Li) detector coupled to a well calibrated Mini-Orange magnetic spectrometer. Precise energies and relative intensities of gamma transitions and conversion electron intensities of gamma transitions have been determined for the first time with better accuracy. The experimental internal conversion coefficients of the gamma transitions in $${}^{169}$$ Tm have been determined using Normalized Peak to Gamma method and compared with the theoretical values adopted by Nuclear Data Sheets to assign multipolarities of all the transitions. The precise internal conversion electron intensities of the low energy transitions can be used as standards for calibration purposes of electron detectors and spectrometers.

Electron spectrometer for electric monopole (E0) transition studies in nuclei

The study of electric monopole (E0) transitions between two 0+ states is important because the monopole strength carries vital information about the nuclear structure due to its direct link with the mean squared charge radius r2 and quadrupole deformation parameter β. Therefore, the measurement of internal conversion electrons (ICE) or internal pair formation (IPF) is crucial for E0 transition studies. Transitions between 0+ states do not change angular momentum. Hence, single-photon emission is forbidden, but can decay by conversion electrons or pair formation and two-photon emission which is mostly negligible. In order to implement E0 studies at iThemba LABS, an electron spectrometer that uses a solenoidal magnetic field acting as a lens and a Si(Li) detector has been refurbished and characterized using calibration sources of ICE. Figures of merit have been extracted and compared with simulations. The spectrometer coupled with an array of LaBr3:Ce detectors and Low Energy Photon Spectrometers (LEPS) was successfully implemented for in-beam experiments. Measurements of internal conversion coefficients (ICC) and monopole strengths extracted from in-beam measurements of 72As, 72Ge, and 72Se are presented.

First identification of high-spin states in the odd-odd neutron-rich nucleus152Pr

The odd-odd neutron-rich nucleus ${}^{152}$Pr has been studied from the spontaneous fission of ${}^{252}$Cf with Gammasphere. A high-spin level scheme of ${}^{152}$Pr has been established for the first time. Angular correlation and internal conversion coefficient measurements are used to determine the transition multipolarities. The possible configurations of the bandhead have been discussed based on systematics and total Routhian surface calculations.

Prolate-oblate shape coexistence in 75Kr

The collective bands of 75Kr were extended up to spin 45 2 using the compound reactions 50Cr( 28Si,2pn), 54Fe( 24Mg,2pn) and 58Ni( 20Ne,2pn) 75Kr. Lifetimes were measured by RDDS with nine OSIRIS detectors in coincidence. Mixing ratios were determined by measurements of internal conversion coefficients, angular distribution and correlations. Deviations between different measurements are explained by the short lifetimes leading to angle dependent intensity losses due to Doppler shift. Spins and parities were assigned from angular distributions, excitation functions and DCO ratios measured with the OSIRIS_12 spectrometer. The band head spin of the negative parity yrast band was established as 3 2 via DCO ratios and internal conversion coefficients. Further bands at low excitation energy were found. In accordance to Woods-Saxon cranking model calculations, these weaker populated sidebands are interpreted to be built on oblate deformed intrinsic states ( β 2 ≈ −0.2), while the strongly populated bands are built on prolate deformed states ( β 2 ≈ +0.4). The interpretation of the 1qp g 9 2 yrare band, to be generated from oblate deformation, is further supported by ΔI = 0 transitions into the yrast band and a similar oblate deformed g 9 2 structure in the isotone 73Se. The experimental level energies, branching ratios, transition probabilities and mixing ratios are compared to rotor model calculations. The deviations between experiment and rotor model calculations are interpreted to be based on mixing between prolate and oblate states.

Study of excited levels in 149Pm

Excited states in 149Pm have been studied through the 150Nd(d, 3n) reaction. γ-γ and electron-γ coincidence data have enabled partial level and decay schemes to be extended up to spin ( 27 2 ). The spins and parities of excited levels have been deduced from measurements of internal conversion coefficients, decay schemes, and from comparison to the N = 88 isotones 151Eu and 153Tb. The data are discussed in terms of the strength of octupole correlations.

Parities and multipolarities of gamma rays in neutron-rich odd-mass Ba nuclei

The nuclei 143,145,147Ba produced in the spontaneous fission of 248Cm have been studied using the EUROGAM phase II array. The parities and multipolarities of γ rays in these nuclei have been assigned from triple angular correlation, directional linear-polarisation correlation and internal conversion coefficient measurements. These data confirm an alternating-parity sequence connected by strong electric dipole transitions in 143Ba. They also reveal a more weakly populated, complementary alternating-parity sequence. The two sequences together exhibit some characteristics of parity-doublet bands. Interpreting the E1 strengths in terms of a rotating intrinsic dipole moment gives a moment similar in size to that observed in 142Ba and 144Ba. No well-developed similar structure is seen in 145Ba, although E1 transitions are observed, from which a value of the dipole moment is obtained. This value is smaller than the moment observed in 143Ba. No features appropriate to strong octupole correlations were observed in 147Ba.

A compact apparatus for alpha - gamma , alpha -eK,L,M angular correlation and internal conversion coefficient measurements

The authors have designed a versatile and compact system which allows the simultaneous measurements of alpha - gamma and alpha -eK,L,M angular correlations and hence allows the determination of internal conversion coefficients. The capability of the system is illustrated by applying it to the study of the 227Th to alpha 223Ra* decay.

Conversion electron and yrast state measurements in 73Br.

Gamma-ray and conversion electron measurements have been performed in the reactions {sup 58}Ni({sup 24}Mg,2{alpha}{ital p}){sup 73}Br at 110 MeV and {sup 40}Ca({sup 36}Ar,3{ital p}){sup 73}Br at 130 MeV, respectively. From {gamma}{gamma} coincidence data the previously known level scheme was confirmed and extended up to probable spin {ital I}=45/2. In the conversion electron spectra, the decay of the previously postulated 27 keV state was observed for the first time. From the measurement of internal conversion coefficients, multipolarities of seven transitions in the bandhead region of {sup 73}Br were determined and allowed spin-parity assignments to be established. High spin properties and quasiparticle alignment effects are discussed in comparison with {sup 75}Br.

124Ba Decay to the 55 124 Cs69 low-spin levels

The decay of124Ba to the levels of odd-odd124Cs has been studied with on-line mass-separated sources delivered at the Isocele facility. The energy level scheme has been established fromγ-ray singles,γ−γ−t coincidence ande−γ−t coincidence spectra. Spin and parity of several low-lying levels have been assigned on the basis of internal conversion coefficient measurements andβ-branchings. A completely new level pattern including approximately 50 levels and 180γ-rays is proposed for124Cs. Several features of this level scheme are discussed and compared to those of neighbouring isotopes.

Measurement of internal-conversion coefficients of 122- and 136-KeV gamma transitions in57Co decay

Measurement of internal-conversion coefficients of 122- and 136-KeV gamma transitions in57Co decay

Decay of 0.61-sBa148to levels of odd-oddLa148

The decay of1 /sub 56//sup 48/Ba/sub 92/ to levels of odd-odd 1 /sub 57//sup 48/La/sub 91/ has been studied in experiments where ..gamma..-ray singles, time-dependent ..gamma..-ray spectra, and ..gamma gamma..t coincidence spectra were collected. The /sup 148/Ba activity was produced directly by on-line mass separation. The half-life of /sup 148/Ba was determined to be 0.61 +- 0.03 s. A level scheme containing 26 levels and 63 ..gamma.. rays is proposed for /sup 148/La. Spin and parity for several low-lying levels are assigned on the basis of internal conversion coefficient measurements and ..beta..- and ..gamma..-ray branching. A half-life of 67 +- 4 ns is measured for the 56-keV level. Several features of the level scheme are discussed and compared to neighboring La isotopes and N = 91 isotones.

The level structure of 96Y from the decay of 96Sr

The 1s β − decay of 96Sr was studied with γ-γ coincidences, internal conversion coefficient measurements and γγ(θ) angular correlations. The 96Sr activity was obtained as a result of β − decay of 96Rb which was produced by the OSTIS mass separator. The α k internal conversion coefficients were determined for 5 of the most intense transitions between levels in 96Y. Angular correlations were deduced from gammas coincident with the 122.3 keV and 530.0 keV transitions in 96Y. A level scheme of 96Y is proposed and definite spin-parity assignments are made for 5 levels. The scheme is discussed within the context of level systematics of odd-odd Y isotopes.

In-beam measurements of internal conversion coefficients

In-beam measurements of internal conversion coefficients

Internal conversion coefficient measurements for transitions inCs140from the decay ofXe140

Internal conversion coefficient measurements for transitions in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Cs</mml:mi></mml:mrow><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>140</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>from the decay of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Xe</mml:mi></mml:mrow><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>140</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>

Relative intensity and internal conversion coefficient measurements in the decays of 51Cr, 137Cs, 192Ir, and 207Bi

An “internal conversion coefficient spectrometer” utilizing Ge(Li) and Si(Li) detectors has been used to make precision measurements of relative gamma-ray intensities for transitions following the decay of 192Ir and 207Bi, relative internal conversion line intensities for some transitions from 192Ir, and conversion coefficients for some transitions from the decays of 51Cr, 137Cs, and 192Ir. Limits and values are given for E2 M1 mixing ratios and penetration effects for the 320.1-keV transition in 51V, the 484.5-keV transition in 192Os, and the 604.4-keV transition in 192Pt. The consequences of the results for nuclear structure are discussed.

Levels in189Os populated in the decay of189Re

The excited level scheme of189Os as populated by the decay of 23.4-h189Re has been studied by use of Ge(Li) and Si(Li) detectors in the γ-ray singles and coincidence mode. The data confirm the presence of excited levels in189Os at 30.8 (Jπ=9/2−), 36.2 (1/2−), 69.5 (5/2−), 95.2 (3/2−), 216.7 (7/2−), 219.4 (7/2−), 233.6 (3/2−), 275.8 (5/2−), 496.8 (1/2−, 3/2+) and 599.8 (1/2−, 3/2+) keV. The spin and parity assignments are based on multipolarities determined by internal conversion coefficient measurements and decay systematics. A decay scheme is established for189Re which accommodates 98% of the electromagnetic transition intensity. No evidence for the 150-d189Re isomer was found in this study.

Low- K bands in 176Hf populated in the (α, 2n) reaction

Levels in 176Hf have been studied by the 174Yb(α, 2n) 176Hf reaction. The observation of γ-rays both in singles and coincidence experiments, and the measurement of internal conversion coefficients of many of these transitions has led to the assignment of eleven rotational bands. Those bands with low K are discussed in this paper. They are the ground state band, a K π = 0 + band at 1150 keV,a K π = 2 − band at 1247.5 keV, a third K π = 0 + band at 1293 keV, a K π = 2 + at 1341.1 and finally a K π = 3 + band at 1577.3 keV. The properties of these bands will be discussed. In particular, a suggested explanation for the unusual decay pattern of the K π = 2 − band will be presented.

A compact electron spectrometer for in-beam measurements of internal conversion coefficients

A compact magnetic spectrometer for measuring electron conversion coefficients is described. A very efficient method to subtract the activation background, based on a pulsed beam-coincidence technique is also presented and discussed. The chosen angle of detection for the electrons avoids the ambiguities present in previous methods and allows straightforward assignments of transition multipolarities in a number of specified cases.

K- andL-shell internal conversion coefficients of the 256 and 139 keV γ-transitions from151Nd

A Ge(Li) gamma-ray spectrometer and a Si(Li) electron spectrometer were standardized for internal conversion coefficient measurements using gamma-transitions of well-determined αK andK/L values from standard sources. The internal conversion coefficients of four gamma-transitions following the 12 minute β-decay of151Nd were determined by using this standardized spectrometer.