Internal Conversion Spectrum Research Articles

The internal conversion spectrum following 244Cm alpha-particle decay

The internal conversion spectrum following the alpha-particle decay of 244Cm was studied using the National Physical Laboratory (NPL) π√2 beta-spectrometer. Conversion lines from the two most intense transitions were identified as consistent with the multipolarity assignment of E2. Upper intensity limits were set for a third transition which were also in accord with a multipolarity of E2.

Calibration of the isomer shift of125Te from internal conversion and mössbauer measurement

Radioactive125I was ion-implanted into 7 different metal matrices. Al, Au, In, Pt, Sn, Te and Zn, and internal conversion and Mossbauer spectra associated with the 35.46 keV M1 transition of125Te were measured for the same samples. A value ΔR/R=(0.853±0.115)×10−4 was derived for the relative difference of the nuclear charge radius for the 35.46 keV M1 transition of125Te.

Levels in 81Kr populated by the [formula omitted] reaction

Levels in 81Kr have been studied by the 81 Br(p, nγ) reaction at proton energies from 1.80 to 5.00 MeV. Gamma-ray excitation functions, γ-γ and n-γ coincidence spectra and an internal conversion spectrum have been taken. A level scheme of 81Kr has been proposed, and spins and parities have been assigned to many low excited states. The half-life of the first excited state (49.4 keV) has been measured to be 8.4±1.0 ns. A simple shell model calculation assuming a 88Sr core has been carried out and compared with the experimental results.

Internal conversion study on the contact charge density of57Fe impurity atoms in Au metal

Three different internal conversion spectra were measured on the 14.4 keV transition of57Fe in Au metals. Adaptability of our method for analysing the line intensity, i.e. the deconvolution-reconvolution method with the constant tail fraction rule was tested experimentally. The obtained 4s electron densities, ρ4s(o), of Fe impurity atoms in Au agreed on four samples within the error. The weighted mean value of ρ4s(o) of Fe in Au is 4.98±0.68a 0 −3 . It is concluded that the method of analysis is reasonable in this type of experiment.

Study of167 Yb levels excited in the decay of167Lu

The167Lu source was isolated from products of spallation reaction induced by 660 MeV protons on tantalum target. The direct and the prompt coincidence spectra of gamma rays from the167Lu decay have been studied with different Ge(Li) detectors. Half-lives of several excited states in167Yb have been measured using the delayed coincidence technique. The internal conversion spectra were investigated with Si(Li) detector and with permanent magnet spectrograph as well. The energies and intensities of more than 400 gamma-transitions were determined. The multipolarities of 225 gamma-transitions were established. The proposed decay scheme of the167Lu is based on coincidence measurements, the analysis of energy sums and reaction data. The states in167Yb are interpreted in terms of the unified model. The role of the Coriolis coupling is discussed.

Collective states fed by weak α-transitions in the 230U chain

The 230U decay chain has been investigated using Ge(Li) spectrometers in singles and coincidence measurements. The internal-conversion spectra have been studied in a β-spectrometer with a Si(Li) detector placed in a homogeneous magnetic field. A total of 31 γ-ray transitions, 14 of which have not been reported before, have been observed in the decay of 230U and its descendants. All transitions could be unambiguously placed in the individual level schemes. The new band-heads at 805 and 914 keV in 226Th and 222Ra, respectively, are proposed as 0+ quadrupole-pairing vibrations. No evidence has been found for the existence of 0+ two-phonon harmonic octupole states in these nuclei. A possible anharmonicity of the octupole vibrations is discussed.

Nuclear structure of194Pt

The decay of194Ir has been thoroughly studied resulting in the construction of a decay scheme consisting of 26 excited states and 69 transitions. Nine new levels and 29 new transitions were added to the previously known scheme. Of these, levels at 1,893.6 and 2,053.0 keV as well as 9γ-ray transitions are new to the194Pt level scheme. Preciseγ-ray energy and intensity measurements as well as quantitative coincidence measurements were performed, and the internal conversion spectrum was investigated with a Si(Li) detector. Directional correlation measurements were performed for selected cascades with the major result being the unique assignment of 0+ to the new level at 1,893.6 keV. The structure was interpreted within the framework of the PPQ model as well as the effective-core picture including nuclear triaxiality.

Decay of 72As to the levels of 72Ge

The decay of 72As has been investigated in a further study of the properties of the 72Ge levels. Gamma-ray singles and coincidence spectra were measured with two Ge(Li) detectors coupled to a two-parameter analyzer, and internal conversion spectra were measured with a Si(Li) detector. There were 60 transitions observed, and 55 of these were fitted into 27 excited states in 72Ge at 691.2, 834.00, 1463.96, 1728.27, 2064.82, 2402.2, 2463.80, 2514.71, 2755, 2939.90, 2943.5, 3035.74, 3094.2, 3325.0, 3337.7, 3341.8, 3419.5, 3455.28, 3550.7, 3678.1, 3708.6, 3803.7, 3816.1, 3872.0, 3983.8, 3985.8 and 3995.0 keV. Some of the properties of the low-lying levels in 72Ge may be interpreted in terms of a vibrational model.

Lifetime and decay of the 23.8 keV state of 119Sn

The half-life of the 23.8 keV state in 119Sn was measured by the delayed-coincidence technique. The observed value τ 1 2 = 17.75 ± 0.12 ns corresponds to a natural line width for the state of Γ = 0.325 ± 0.002 mm sec . The internal conversion spectrum was measured; the ratios of internal conversion lines for both the 23.8 and 65.3 keV transitions agree with theoretical predictions and previous experiments.

Studies in the decay of 131Ba revealing nuclear penetration effects in the 92 keV transition in 131cs

The γ-ray and internal conversion spectra of the decay of 131Ba to levels in 131Cs were investigated using a Ge(Li) detector and a double-focussing β-ray spectrometer. Accurate transition energies and internal conversion coefficients were deduced using the internal conversion data of Horen et al. 1) in conjunction with the results obtained here. Gamma-gamma and electron-γ directional correlation measurements were performed. Unique spin-parity assignments were obtained for all levels in a compiled level scheme using the deduced conversion coefficients, the results from angular correlation measurements and the deduced log ft values. Nuclear penetration effects were found to be present in the 92 keV transition characterized by λ = 23 −11 +7.

High resolution studies of transitions in the decay chain146Gd to146Eu to146Sm

Transitions in146Eu and146Sm were studied using a double-focussing beta-ray spectrometer and a Ge(Li) detector. Internal conversion and gamma-ray intensities were determined. The internal conversion spectrum of the three 155, 115 and 116 keV cascading transitions in146Eu was studied for all subshells.K-,L- andM-subshell ratios were determined andE2/M1 mixing ratios were deduced for these three transitions. Intensities from theN- andO+P-shells were determined and compared to theoretical calculations. All internal conversion intensities were found to be in agreement with theoretical data for pureM1 character with smallE2 admixtures for all the three transitions. Selected parts of the internal conversion spectrum of the transitions in146Sm were restudied at 0.06% momentum resolution. This study was mainly concentrated on four transition doublets feeding and deexciting the close lying levels at 1,380 and 1,381 keV. A new transition with 702.20 keV energy was detected in the 702–703 keV transition group. Internal conversion coefficients were deduced using reported gamma-ray intensities. Multipole characters of the transitions were deduced and used as a basis for a discussion of the spins and parities of the lower lying excited states of146Sm.

Internal conversion studies of transitions in96Mo

The internal conversion spectrum from the decay of96Tc has been investigated using a 50 cm radius double-focussing beta-ray spectrometer. Relevant features of the internal conversion spectrum from the decay of96Nb have also been reexamined in the same way. Special interest has been focussed on investigating a proposed doublet level structure at about 2.44 MeV and higher lying levels in96Mo. Internal conversion coefficients have been obtained for most transitions by combining the measured conversion electron intensities obtained in this work with recently reported gamma-ray intensities from Ge(Li) detector measurements. A level scheme has been compiled and deduced transition multipolarities have been used for a discussion of spins and parities for the levels.

A cylindrical surface barrier detector for use in a six-gap beta ray spectrometer

The use of a cylindrical surface barrier diode as the electron detector in a six gap beta ray spectrometer is found to make a substantial improvement to the quality of in-beam internal conversion electron spectra. The method of manufacturing the diode is described in some detail and its characteristics are presented. A closed loop electronic system has been used to keep the electron peak in the detector pulse height spectrum within the window of a single channel analyser during the point by point scanning of an internal conversion spectrum.

γ Transitions in the Decay of 99Mo

Abstract The internal conversion spectrum of γ transitions in the decay of 99Mo has been re-studied using a high resolution double focusing β-ray spectrometer. In addition to γ-rays previously reported, seven more γ-rays could be observed. Internal conversion coefficients and multipolarities of γ transitions are given. Energies, spins and parities of high excited levels in 99Tc are confirmed.

The apparent variation of the measured K/LMN ratio with source-silicon detector geometry

While using LIDS detectors for measuring internal conversion spectra in which the L, M and N lines were not resolved, a striking decrease in the K/LMN ratio was observed as the solid angle, Ω, subtended by the detector at the source, was increased. This observation is explained by assuming the presence of coincidences in the detector between K-electrons and their associated K-X-ray photons. Calculations of the K/LMN ratio as a function of Ω based on this assumption, are shown to be in good agreement with experimental values. For 137Cs the measured ratios at Ω = 0.025π and Ω = 1.66π sterad give values of 4.30 and 1.89 respectively and for 109Cd the ratios at these angles give 0.76 and 0.40 respectively, where ratios at Ω = 0.025π are the “true” values. The implications of the results for electron spectroscopy are discussed and a method of making use of the coincidence effect for measuring electron collection efficiencies, is suggested.

The decay of 99Mo

The radioactive decay of 67 h 99Mo has been studied by measuring internal conversion spectra, single gamma-ray spectra and gamma-gamma coincidences. Large volume Ge(Li) detectors, a curved-crystal spectrometer, a sector field beta-ray spectrometer and a fast coincidence arrangement were employed in these experiments. The following gamma rays were observed (relative intensities are given in parentheses): 40.584 ± 0.002, 140.511 ± 0.006(100), 142.63 ± 0.03(0.03), 181.06 ± 0.04(7.5), 249 ± 1(0.006), 344 ± 2(0.0013), 366.4 ± 0.1(1.6), 380.7 ± 0.2(0.011), 409 ± 2(0.0016), 411.5 ± 0.5(0.027), 458 ± 1(0.006), 528.9 ± 0.2(0.06), 620.7 ± 0.2(0.027), 620.7 ± 0.2(0.005), 739.7 ± 0.1(15.4), 778.2 ± 0.1(5.4), 823.1 ± 0.1(0.16), 961.0 ± 0.2(0.12), 988.2 ± 0.5(0.002), 1001.7 ± 0.2(0.007) and 1016 ± 2 keV(0.001). The following energy levels are populated: 140.511 ± 0.006, 142.63 ± 0.03, 181.095 ± 0.007, 509.0 ± 0.1, 671.5 ± 0.2, 761.3 ± 0.2, 920.8 ± 0.1, 1004.2 ± 0.2, 1129.7 ± 0.2, 1142.1 ± 0.2, 1169.3 ± 0.5 and 1197 ± 2 keV. The levels at 671.5, 761.3, 1004.2, 1142.1, 1169.3 and 1197 keV have not been reported previously. The following K-conversion coefficients were determined: α K(140.5) = 0.104 ± 0.007, α K(142.6) = 23 ± 6, α K(181.1) = 0.130 ± 0.012 and α K(739.7) = (1.6 ± 0.4) × 10 −3.

Nuclear spectroscopy in the neutron-deficient 173 ≦ A ≦ 185 region

The internal conversion spectra of deformed nuclei in the mass interval 173 ≦ A ≦ 185 were investigated with permanent magnet spectrographs. By combining the conversion results with complementary data from independent photon studies, partial decay schemes are deduced from energy sums, multipolarities and intensities of the transitions. The quantum numbers of nuclear energy levels are associated with intrinsic and collective modes of excitation in the framework of the Nilsson and Bohr-Mottelson models. Parameters relevant to rotational configurations and branching ratios of the de-exciting transitions are evaluated. The energy systematics of proton and neutron particle states in odd-mass nuclei is correlated with the particle-coupled spectra in adjacent doubly odd nuclei. More complete conversion electron measurements permits extension of nuclear level structures of 148, 146Sm.

La Désintégration 109Cd→ 109Ag

The 88 keV transition in 109Ag has been studied by means of a double-focussing magnetic β-spectrometer and of a solid-state Ge(Li) detector. By comparison with the 84 keV transition in 170Yb, the energy was found to be 88.09±0.03 keV and the internal conversion coefficient α K=12.7±0.9. The internal conversion spectrum has been recorded. All internal conversion measurements agree very well with a pure E3 assignment and theory. The fluorescence yield deduced from the Auger spectrum is ω K=0.834±0.018.

The decay of 90Nb

The decay of 14.60±0.05 h 90Nb has been investigated with a double-focussing iron-yoke spectrometer and with a Ge(Li) detector. The end-point energy of the intense (53±6%) positon branch has been determined to be 1500±4 keV, leading to a Q-value of 611±5 keV. Some 17 transitions have been found in the internal conversion spectrum, and among these are six not previously reported at 518, 828, 1575, 1717, 1914 and 2223 keV. The K-conversion coefficients have been determined by combining the internal conversion intensities with the gamma-ray intensities. For many transitions, probable multipolarity assignments have been obtained from these coefficients and also from K/ΣL and L I/(L II+L III) ratios. The M-conversion intensities of the 133 and 141 keV transitions have been found to be in agreement with the recent tabulations of Hager and Seltzer. All transitions observed have been fitted into a tentative decay scheme, which in its lower part is in agreement with shell-model calculations.

Establishment of an excited state at 1.64 keV in 193Pt

Abstract A nuclear energy level of 1.64 keV in 193Pt has been established in a high-resolution study of the internal conversion spectrum in the 193Au decay. The measured half-life is 9.7 ± 0.6 ns and the de-exciting transition is most probably of M1 character.