W.R. Dixon

Lifetimes of 44Ti Levels

Abstract Lifetimes in 44 Ti have been measured by the attenuated Doppler shift following α-capture in 40 Ca. targets. Mean lifetimes for the 1083 keV (2 + 1 ), the 2454 keV (4 + 1 ), the 2531 keV (2 + 2 ), the 2886 keV (2 + 3 ) and the 3415 keV states of 44 Ti are respectively 4.5 ± 1.1, 0.60 ± 0.11, 1.42 ± 0.20, 0.42 ± 0.14 and 0.70 ± 0.11 ps. The lifetimes of the 1904 keV (0 + 2 ) and 3176 keV states are greater than 0.7 and 3.0 ps, respectively. The level energies and experimental B (E2) values support the vibrational model as a first approximation for 44 Ti. On the other hand the strong 2 + 2 → 0 + 2 transition (24 ± 6 W.u.) suggests the beginning of a rotational band based on a deformed panicle-hole configuration.

Electromagnetic decay of first and second T = 32 states in 19F

Abstract The two lowest T = 3 2 states in 19 F have been found as strong isolated resonances in the 15 N (α, γ) 19 F reaction. Some significant discrepancies are found between the measured transition strengths and those calculated from shell-model wave functions.

Absolute cross section of the K39(n,pp)A39 reaction for 2.5-MeV neutrons

The cross section for the K/sup 3//sup 9/(n,p)Ar/sup 3//sup 9/ reaction, at a neutron energy of 2.46 Mev, is found to be 96 plus or minus 6 mb. The experimental method consists of taking coincidences between the events in a KI(Tl) scintillation crystal and the He/sup 3/ particles that are produced simultaneously with neutrons in the d-d reaction. (auth)

The (n, p), (n, d) and (n, α) reactions induced by 14.6 MeV neutrons in CsI(Tl) scintillation crystals

Abstract The (n, p), (n, d) and (n, α) reactions induced by 14.6 MeV neutrons in CsI(Tl) scintillation crystals have been observed. Pulse shape discrimination has been used to distinguish the various particles, permitting an energy spectrum for each to be obtained. The proton and alpha particle spectra have been analysed from the point of view of the statistical theory of nuclear reactions, but there are left over substantial components which must be attributed to direct interactions. The direct component for protons is estimated to be at least 45 %, and for alpha particles to be at least 38 %. Absolute cross sections have been obtained by the method of “tagging” the neutron beam by its associated particles; the averages for Cs and I are found to be σ(n, p) = 8±1 mb, σ(n, d) = 1.2±0.2 mb and σ(n, α) = 1.8±0.2 mb.

A study of 28Si(α, γ)32S resonances below Eα = 3.83 MeV

Abstract The γ-decays of eleven resonances in the 28 Si(α,γ) 32 S reaction below E α = 3.83 MeV have been studied using a large Ge(Li) detector. Results for branching ratios differ considerably from previous NaI work. The previous discrepancy in radiative strengths for the 2.61 MeV resonance is explained by this data. The strengths of the first five resonances at E α = 1.77, 1.99, 2.19, 2.37 and 2.42 MeV appear to be (39 ± 13)% lower than previously reported. Spin-parities of l − , 2 + and 2 + have been assigned to the levels at 8.50, 8.69 and 8.86 MeV respectively. The radiative width of the E p = 1.467 MeV, J π = 3 − resonance in the 31 P(p,γ) 32 S reaction has also been measured.

The Ge73(n, α)Zn70 reaction at 14 MeV observed in a lithium drifted germanium detector

Abstract : The (n, alpha) reactions induced in germanium by 14 MeV neutrons have been observed in a germanium semiconductor detector. Values of the cross section of the ground-state transition of Ge73(n, alpha)Zn70 at 14.1 and 14.8 MeV are presented along with possible evidence for the existence of excited states of Zn70 at 1.95=0.1 MeV and at 2.3=0.1 MeV. Evidence for a reduced response of the detector to the Zn recoil atoms is discussed. (Author)

The mass and energy levels of 44Ti

Abstract Energy levels of the self-conjugate nucleus 44Ti have been studied with the 40 Ca (α, γ) 44 Ti reaction. A shell-model calculation of levels in 44Ti and 44Sc has been performed for comparison purposes.

Energy and angular distributions for the Al27(n, α)Na24 reaction with 14 MeV neutrons

Abstract The Al 27 (n, α)Na 24 reaction at a neutron energy of 14.1 MeV has been studied by the nuclear emulsion technique. As a result of careful shielding of the emulsion, a thin aluminium target could be used and it was possible to achieve an energy resolution of 4% at 9 MeV. The energy distribution of the alpha particles shows peaks corresponding to the first few energy levels in the residual Na 24 nucleus. The emission of the low energy alpha particles is nearly isotropic, while in the higher emnergy region there is some preferential emission in the forward direction. Analysis of the energy and angular distributions indicates that the statistical theory is adequate to account for most of the alpha particles. The value of the spin cut-off parameter for the energy interval 4–7 MeV is found to be 2 σ 2 = 16± −5 +∞ . The effect of Ericson fluctuations in the statistical analysis is discussed briefly. The background tracks have also been examined: high-energy alpha particles from heavy constituents of the emulsion are peaked strongly forward; low-energy alpha particles from light constituents are peaked in both the forward and backward directions.

Identification and decay properties of the fourth Kπ = 0+ band 168Er

Abstract The fourth K π = 0 + band with bandhead at 1833.5 keV in 168 Er has been identified by combining ( n , γ ) and (n,e − ) data with the results of (t,p) reaction spectroscopy. Possible interpretations of the new band are advanced.

Lifetime of the 103 keV level in 93Np237

Abstract : The half-life of the 103 keV level in 93Np237 has been found to be (8=4) X 10 to the -11th power sec. The experimental method utilizes the Doppler shift of 26 keV conversion electrons emitted from the 103 keV level following alpha decay of Am241. These electrons are examined in a high resolving power beta-ray spectrometer. The distribution of electrons is compared with the distribution obtained when the conversion electrons are successively decelerated and accelerated by an electrostatic field near the source. A finite lifetime results in a net acceleration of the conversion electrons. A method of analysis has been developed which enables the lifetime to be measured in terms of the resulting distortion of the original distribution. (Author)