S.-E. Karlsson

A 50-cm double focusing beta spectrometer of the current sheet type

Abstract A precision beta spectrometer is described. It is an air-cored, double focusing, instrument in which the magnetic field is generated by two coaxial cylindrical coils. Easy access is provided to the source and detector positions and there is sufficient space for electron-gamma coincidence arrangements. The solid angle accepted by the spectrometer is 0.3% of 4π at a resolution of 0.2%, and 0.05% at a resolution of 0.02%. Current regulation and data recording are completely automatic as well as the cooling system for the spectrometer coils. The maximum electron energy of the instrument is 3.5 MeV. A special laboratory has been built and great care has been taken to provide a magnetic field-free space in the spectrometer room. A relative width of 0.012% is obtained for the I-line of ThB. With a mass-separated source of Xe 133 , a conversion electron spectrum from the K, L, M and N shells is obtained in which eight components are observed at a resolution of 0.04%.

L subshell ratios in some pure E2 transitions

Abstract The L subshell conversion line intensity ratios have been studied for four 2 + → 0 + transitions (86.79 keV in 66 160 Dy, 80.57 keV in 68 166 Er, 84.26 keV in 70 170 Yb and 100.09 keV in 74 182 W) and for the 5 2 − → 1 2 − 99.07 keV transition in 74 183 W. The L II /L III ratios obtained agree very well with theory but the L I /L II and L I /L III ratios are 5–9% higher than the theoretical ratios. Deviations of the same magnitude have also been reported by other research groups.

The decay of 140La

Abstract The beta-ray and internal-conversion spectra from the decay of 140 La to 140 Ce have been investigated using double-focussing spectrometers. Beta branches with end-point energies 2166±7, 1674 ± 10, 1354 ± 15 and 1244 ± 20 keV have been established, giving a Q -value of 3762 ± 8 keV. In the internal conversion spectrum, 26 transitions have been found ranging in energy from a previously not reported 24.595 ± 0.004 keV transition up to a very weak transition at 3322 ± 4 keV. The gamma-ray spectrum following the decay of 140 La has been studied using a Ge(Li) detector. The theoretical K-conversion coefficient for the 1596 keV E2 transition has been used to calculate conversion coefficients. From these coefficients together with K//∑L and L-subshell ratios, probable multipolarity assignments have been obtained for most of the transitions. All transitions observed have been fitted into a tentative decay scheme.

The low-energy internal conversion spectrum of 182W from the decay of 182Ta

Abstract The internal conversion spectrum of low-energy transitions in 182W following the decay of 182Ta has been studied using the 50 cm, iron-free spectrometer at Uppsala. Relative conversion line intensities are given together with internal conversion coefficients, multipolarities and mixing ratios. The energies of the 32 and 43 keV transitions have been determined with high precision. The existence of two previously reported transitions could not be confirmed.

Array detectors and extended source used in a double focusing beta spectrometer

Abstract The 50-cm iron-free beta spectrometer at Uppsala has been furnished with an array of close-lying semiconductor detectors and an extended source arrangement. The combined detector and source system increase the amount of information per time-unit more than 100 times. A description of the detector and source arrangements is given together with some applications.

Precision measurements on the 296 keV and 316 keV transitions in 192Pt

Abstract A recently reported L II anomaly in Pt is removed. Precise determinations of the energies of the 296 keV and 316 keV transitions are obtained. The L subshell ratios for the 316 keV E2 transition are measured.

The decay of 191Au and the level scheme of 191Pt

Abstract A total of 84 transitions in 191 Pt have been established by studying the internal conversion spectrum following the decay of 191 Au with high-resolution, magnetic, beta spectrometers. Multipolarities and mixing ratios for the strongest transitions have been deduced from K/L ratios and/or L subshell ratios. The high accuracy of the transition energy determinations together with calculated total transition intensities, established multipolarities and information from coincidence experiments enabled the construction of a consistent level scheme comprising 25 excited levels and 69 transitions. This level scheme deviates greatly from that proposed by Marklund et al. 5 ).

Determination ofL subshell ratios of pureM1 transitions

L subshell ratios have been accurately measured for two pureM1 transitions, 82.5 keV in67166Ho and 238.6 keV in83212Bi. The results for all ratios are in fairly good agreement with those obtained from the theoretical calculations bySliv andBand.

Relative internal conversion electron intensities of the 113 keV transition in 177 Hf

The intensities of the internal conversion lines of the 113 keVM1 +E2 transition in177Hf have been measured. From comparison with theoretical conversion coefficients the transition has been found to be (95.2 ± 0.5)%E2 corresponding to ¦δ¦=4.5 ± 0.3. The theoreticalLI andMI conversion coefficients used in the comparison have been increased by 5% according to the result that for pureE2 transitions in the deformed region theLI/LII,LI/LIII,MI/MII, andMI/MIII theoretical ratios are too low (∼5%). Moreover, the present result indicates that theLII/LIII andMII/MIII ratios obtained from the tabulations by Hager and Seltzer and from the computer program by Pauli are too high (1–2%).