Ong Ping Hok

The beta-decay of 233Pa

Synopsis Further measurements on the electron spectrum of 233Pa have been performed. 14 gamma transitions were determined from the observed conversion lines. A very weak indication was found of an electron line at 360 keV which might be the K-conversion line of a 475.6 keV transition. The Fermi-Kurie analysis led to three partial beta-spectra with endpoints of 568 ± 5, 257 ± 5 and 145 ± 10 keV and intensities of 5%, 58% and 37% respectively. These results agree with the decay scheme proposed by B r o d i e. e− and β− coincidences were also performed.

The decay of the UX-complex

Synopsis The radiations of the UX-complex and of pure UZ were reinvestigated by means of a double-focusing beta-ray spectrometer and a gamma-scintillation spectrometer. A rapid method was worked out to obtain relative pure UX 2 samples. The gamma-rays were measured with a photographical method. Sixteen gamma-transitions were found in UZ and twelve in UX 2 ; five of these transitions seemed to occur in both decays. From these data and a β—e − coincidence measurement in UX 1 a tentative level scheme of the UX-complex was set up. The UZ-level proved to be the ground state of 234 Pa, 60 ± 15 keV below the UX 2 level.

Measurements on the continuous beta-spectra, the conversion lines and the auger-lines of U(X1 + X2)

Synopsis Measurements on the β-spectra of U(X1 + X2) in a 16.2 cm doublefocusing spectrometer, (resolution of 1.5%) are described. Of the electronlines 25 could be ascribed to 11 γ-rays, while the lines below 21 keV could be interpreted as L-Auger lines on account of energy and intensity considerations. The Fermi-Kurie analysis of the continuous β-spectra gave 5 components with endpoints at 2305, 1500 and 580 keV for UX2 and at 193 and 103 keV for UX1. The relative intensities were respectively 90%, 9% and 1% for UX2 and 66% and 34% for UX1. The 91 keV γ-ray of UX1 is E2, while the 810 keV γ-ray of UX2 may be M1. A tentative disintegration scheme with spin and parity assignments to some of the levels is discussed.

The decay of 90Nb

Synopsis Measurements have been performed on the radiations of 90Nb with a double focusing spectrometer and with a scintillation spectrometer. The positon spectrum consists of three partial spectra with maximum energies of 1.500, 0.865 and 0.55 MeV. Seven γ-transitions have been deduced from the conversion electrons and the γ-scintillation spectrometer measurements. Together with the results of β-e−-coincidence measurements a probable decay scheme has been constructed.

The beta-ray spectrum of 71arsenic

Synopsis The activity of 71 As, obtained by bombarding Ge with deuterons of 26 and 14 MeV has been investigated. From the decay of the electron line of 163,9 keV the half-life was found to be 59,5 ± 2 hours. The 175 keV γ -ray gave the ratio e K − /e L+M − = 8.3. The Fermi-Kurie plot of the positon spectrum allowed two interpretations: a simplex spectrum with endpoint at 800 keV or a complex one with end points at 675 and 850 keV. The two corresponding decay schemes are discussed. Four new electron lines were detected, which were ascribed to L - and M -conversion lines of a 13 keV γ -ray from 73 As, and to K - L , L and K - L , M Augerlines.

On the electron spectra of 232Pa 233Pa and 230Pa

Synopsis Measurements of the β-spectra of the Pa-isotopes, formed by deuteron bombardment of Th have been performed in a 30.0 cm double focusing beta-spectrometer. The Fermi-Kurie analysis of the continuous spectra led to 5 partial spectra in 232Pa with endpoints at 1.24, 0.715, 0.54, 0.37 and 0.26 MeV. The analysis of the spectrum of 233Pa led to 4 components, but is less certain because of the possible influence of 230Pa. A weak positon spectrum was also detected. About 100 conversion lines could be detected, from which 35 γ-rays could be deduced. 15 of these γ-rays belong to 232Pa, 14 to 233Pa and 4 probably to 230Pa. For 232Pa a preliminary decay scheme is proposed, fitting the 5 beta-components and the more intense γ-rays. The data for 233Pa did not allow the construction of a consistent decay scheme.

The beta-radiations of UX1 and UX2

Abstract The complete beta-spectrum of U(X 1 + X 2 ) was measured with a 180° spectrometer. The primary spectrum of UX 1 proved to be decomposable into two components with endpoints at 192 and 104 KeV and intensities 56% and 44%. That of UX 2 showed three components with endpoints at 2320, 1500 and 600 KeV, the intensities being 80%, 13% and 7%. The reality of the 600 KeV component, however, is considered as dubious. The secondary spectrum of UX 1 shows three lines which could be explained by conversion of a 90.4 KeV nuclear gamma-ray in the L I , M I and N I -shell. That of UX 2 consists of two lines, arising by conversion of a 817 KeV nuclear gamma-ray in the K and L I -shell. As far as concerns the values of the energies the results are in good mutual agreement. Serious discrepancies remain between the intensities of the gamma-ray derived from the beta-spectra and those determined by absorption measurements.

The beta-decay of 230Pa

Summary The beta-decay of 230Pa was investigated with a magnetic beta-ray and a scintillation spectrometer. This led to 9 gamma-transitions from which two possible schemes of 230Th could be constructed. A positon spectrum and a negaton spectrum with maximum energies of 0.4 MeV and 0.405 ± 0.02 MeV were also observed. These results, however, are not so certain because of possible contaminations of fission products.