P.M. Endt

The decay of the nuclides 75Se and 75Ge

Synopsis Gamma transitions in the decay of the nuclides 75Se and 75Ge have been investigated by scintillation spectroscopy. Single spectra and coincidence spectra were found to conform with the level schemes constructed by previous authors. Directional correlations of five γ cascades have been measured. Polarization correlation measurements were performed on the 121 keV — 280 keV and 136 keV — 265 keV γ cascades. The following spins and parities have been assigned to levels in 75As: ground state 3/2−, 199 keV ½−, 265 keV 3/2−, 280 keV 5/2t-, 304 keV 9/2+, 401 keV 5/2+.

Continuous and discrete gamma-radiation in the decay of 103Pd

Synopsis The continuous γ-ray spectrum (internal bremsstrahlung) and the discrete γ-rays resulting from the decay of 103Pd by electron capture have been investigated with a scintillation spectrometer. Weak discrete γ-rays have been found with the following energies and intensities: 503 ± 8 keV (0.11 ± 0.02‰), 367 ± 6 keV (0.60 ± 0.07‰), 305 ± 8 keV (0.11 ± ± 0.03‰) and (262 ± 15) keV (0.04 ± 0.02‰). The continuous spectrum has been observed, but accurate determinations of its endpoint, intensity and shape were made difficult by the presence of the discrete γ-rays. From an analysis of observed ft-values the 103Pd spin and parity can be determined as J= 5 2 + and the 103Pd-103Rh mass difference as (557−12+27) keV.

The decay of 115Cdm

Synopsis In the decay of 115Cdm (43 d) several new, very weak, γ transitions have been observed in scintillation single spectra and/or coincidence spectra, with the following energies and intensities (in percents of the intensity of the 935 keV γ ray): 130 ± 5 (0.07), 162 ± 3 (1.3), (206 ± 6) (0.15), 292 ± 5 (0.2), 1130 ± 5 (5.2), and 1420 ± 15 keV (2.0). These γ rays fit into the known 115In level scheme if a new level is assumed at Ex = 1129 keV, excited through a 0.07% β- transition. The γ-γ angular correlation has been measured of the 485–935 keV cascade. From this measurement and from considerations on γ-ray intensities and β-ray ft values, spin and parity assignments of 7/2+, (13/2)+, (ll/2)+, and 9/2+ are made to the 115In levels at 935, 1129, 1290, and 1420 keV, respectively. These levels can be regarded as generated by the removal of a g9/s. proton from 116Sn in its first excited state (Jπ = 2+). From Lawson and Uretskys centre-of-gravity rule the excitation energy is estimated of the missing 5/2+ member of this quintuplet.

Angular distribution and yield of protons from the 10B(d, p)11B reaction (II)

Synopsis In a previous paper (to be quoted as (I)) angular distribution measurements have been described of four proton groups from the B(d, p)B reaction at a deuteron energy of Ed = 0.31 MeV. In the present investigation measurements were added at Ed = 0.20, 0.45 and 0.60 MeV. The differential cross section at ϑ = 120° has also been determined as a function of deuteron energy (Ed = 0.175–0.700 MeV) by means of a proton scintillation spectrometer. The relative intensities of the four proton groups show irregularities at Ed = 0.21 MeV corresponding to a new C resonance level at an excitation energy of 26.93 MeV. Angular distributions have been analyzed into a stripping contribution and a contribution from compound nucleus formation. It is shown that the stripping contribution is large for at least two of the four proton groups down to the lowest deuteron energies. The values found by Butler analysis for the angular momentum transfer ln are in agreement with known spins and parities.

Angular distributions and yield of the reaction 14N(d, p)15N

Synopsis Angular distributions were measured of the 14N(d, p)15N ground-state transition by nuclear emulsion technique at deuteron energies of 0.4, 0.5 and 0.6 MeV. There is reasonable agreement with Butlers stripping theory for ln = 1. The target was prepared by bombarding an aluminum foil with 200 keV nitrogen ions. The relative yield of this reaction has been measured for deuteron energies between 0.25 and 0.675 MeV using a thin-crystal NaI (Tl) scintillation spectrometer for detection of protons emitted at θ = 0° with the deuteron beam. The absolute yield at Ed = 0.5 MeV has also been measured by a scintillation spectrometer. In this case a target was used prepared by sandwiching a thin nylon film of known thickness between two aluminum layers.

Angular distributions of four proton groups from the b10(d, p)b11 reaction

Synopsis Angular distributions have been measured of four proton groups from the B10(d, p)B11 reaction corresponding to transitions to the groundstate (group (0)) and the three lowest excited states of B11 (groups (1), (2) and (3)). A thin target of natural boron was bombarded with 310 keV deuterons and protons were detected by nuclear emulsions placed at 15 ° intervals round the target. Protons of different groups were distinguished by their range in the emulsion. Angular distributions of groups (0) and (2) are peaked in the forward direction while those of groups (1) and (3) are more nearly isotropic. By integration over solid angle total cross-sections were determined. They amount to 48 microbarn for group (0), 18 microbarn for group (1), 76 microbarn for group (2) and 11 microbarn for group (3).

Angular dependence and yield of the Be9(d, p) Be10 and Be9(d, t) Be8 reactions

Synopsis Differential cross-sections have been measured of the Be9(d, p)Be10 and Be9(d, t)Be8 ground-state transitions at five deuteron energies between 0.30 MeV and 0.62 MeV. The proton angular distributions can be developed into series of Legendre polynomials of which the highest term is a4P4 while the developments of the triton distributions above Ed = 0.45 MeV need also the terms a5P5 and a6P6. The total cross-sections of the two reactions are equal within the experimental error below Ed = 0.45 MeV while above this energy the Be9(d, p)Be10 reaction predominates.

On some fluctuation problems connected with the counting of impulses produced by a geiger-müller counter or ionisation chamber

Summary In the present article we shall deal with some quantities which are of importance in counting the kicks of a Geigercounter or ionisation chamber arising from some constant or decaying radioactive source. We will first derive the sensibility and the statistical fluctuations of the counting rate meter, using the direct method first indicated by Ornstein and a more classical method for one special case. We also wish to calculate some of these quantities for the case of a scaling set and a mechanical recorder with finite resolving powers. It is shown that in this case the fluctuations are greater (but not much) than in the case of infinite resolving powers.