M.R. Anderson

University of Melbourne, Melbourne, Victoria, Australia

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Publications (13)22.02 Total impact

  • M.R. Anderson · L.W. Mitchell · M.E. Sevior · D.G. Sargood
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    ABSTRACT: The yields of neutrons from the reaction 25Mg(α, n)28Si and of γ-rays from the reaction 25Mg(α, nγ)28Si have been measured as a function of bombarding energy over the range 1.8–6.3 MeV, and the yield of neutrons from 26Mg(α, n)29Si has been measured over the range 1.8–6.0 MeV. Cross sections for 25, 26Mg(α, n)28, 29Si were extracted from the data and compared with global statistical-model calculations. The agreement is very good. Thermonuclear reaction rates under stellar conditions appropriate for explosive neon burning are calculated and their significance for the nucleosynthesis of rare neutron-rich nuclei is discussed.
    No preview · Article · Aug 1983 · Nuclear Physics A
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    ABSTRACT: Absolute cross sections have been measured for (p, y) reactions on 63CU, 64Ni and 63CU over proton energy ranges of 1,05-3 '25, 1·00-3 ·45 and 1·05-4· 70 MeV respectively, for (p, n) reactions over proton energy ranges from threshold to 3· 25,3' 80 and 4·86 MeV respectively, and for 63CU(p, p')63CU over a proton energy range of 1·05-4'00 MeV. All the data are compared with global statistical model calculations. The agreement, to within a factor of 2, between theory and experiment is regarded as satisfactory for a global code, but the 64Ni data are suggestive of a closed shell effect at Z = 28.
    Preview · Article · Jan 1983 · Australian Journal of Physics
  • L.W. Mitchell · M.R. Anderson · S.R. Kennett · D.G. Sargood
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    ABSTRACT: The yield of γ-rays from the reaction 42Ca(p, γ)43Sc has been measured as a function of bombarding energy over the range 0.63–3.01 MeV, from 44Ca(p, γ)45Sc over the range 0.775–4.00 MeV, from 42Ca(p, p'γ)42Ca over the range 2.24–3.01 MeV, and from 44Ca(p, p'γ)44Ca over the range 1.90–5.03 MeV. The cross section of the reaction 44Ca(p, n)44Sc has been measured from threshold to a bombarding energy of 5.05 MeV by observation of the 1157 keV γ-ray associated with the residual 44Sc activity, and the cross section of the reaction 45Sc(p, n)45Ti has been measured from threshold to a bombarding energy of 4.00 MeV both by observation of the annihilation radiation associated with the residual 45Ti activity and by measurement of the total neutron yield with a wide-angle BF3 tube and paraffin detector. All these data are compared with statisticalmodel calculations and satisfactory agreement is achieved. Thermonuclear reaction rates for the (p, γ) and (p, n) reactions are calculated for the temperature range 5 × 108-1010K and the significance of these results for explosive nucleosynthesis in stars is discussed.
    No preview · Article · May 1982 · Nuclear Physics A
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    ABSTRACT: The yield of γ-rays from the reaction 41K(p, γ)42Ca has been measured as a function of bombarding energy over the range 0.68–2.48 MeV and from the reaction 41K(p, αγ)38Ar over the range 1.20–2.48 MeV, and the yield of neutrons from the reaction 41K(p, n)41Ca has been measured from threshold to a bombarding energy of 2.48 MeV. The energy dependence of the cross sections is compared with statistical-model calculations with global optical-model parameters in all particle channels. The calculations seriously overestimate the cross section for the neutron channel and underestimate those for the other channels. A reduction in the imaginary well depth in the neutron channel leads to good agreement with all the data. Statistical-model calculations with this modified set of parameters are then carried out to provide cross sections for the astrophysically interesting reactions 41Ca(n, p)41K, 41Ca(n, α)38Ar, and 41Ca(n, γ)42Ca. Thermonuclear reaction rates are calculated for all six reactions over the temperature range 5 × 108–1010K which includes the range of temperatures of interest in nucleosynthesis calculations.
    No preview · Article · Apr 1982 · Nuclear Physics A
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    ABSTRACT: The strengths of resonances in 25Mg(p, gamma)26Al have been measured in the energy range Ep = 600-1730 keV. Several serious disagreements with previously published results are reported. Thermonuclear reaction rates are calculated for the temperature range (0.5-10) × 109 K for production of 26Al in its ground state and in its isomeric first excited state. Total thermonuclear reaction rates are compared with those calculated from statistical-model cross sections and, even in energy ranges where the experimental cross section derives from widely spaced resonances, the agreement is very good. The establishment of a thermal population of 26Al excited states in a stellar environment is discussed, with both electromagnetic transitions and proton inelastic and superelastic scattering as the thermalising processes.
    No preview · Article · Jan 1982 · Nuclear Physics A
  • S.R. Kennett · L.W. Mitchell · M.R. Anderson · D.G. Sargood
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    ABSTRACT: The yield of γ-rays from the reaction 46Ti(p, γ)47V has been measured as a function of bombarding energy over the range 0.72–3.00 MeV, from 47Ti(p, γ)48V over the range 0.74–3.50 MeV, and from 48Ti(p, γ)49V over the range 0.72–4.40 MeV. The yields of γ-rays following (p, p') reactions on all three targets were also measured and (p, p') cross sections were deduced for the first excited state proton groups for 46Ti and 48Ti and for the first ten proton groups for 47Ti. The yield of neutrons from the reaction 47Ti(p, n)47V has been measured over the range from threshold to 4.40 MeV. All these data are compared with statistical-model calculations, and good agreement is achieved. Thermonuclear reaction rates for the (p, γ) and (p, n) reactions are calculated for the temperature range 5 × 108–1010 K which includes the range of temperatures of interest in nucleosysnthesis calculations.
    No preview · Article · Sep 1981 · Nuclear Physics A
  • S.R. Kennett · L.W. Mitchell · M.R. Anderson · D.G. Sargood
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    ABSTRACT: The yields of γ-rays from the reactions 52Cr(p, γ)53 Mn and 52Cr(p, p′ γ)52Cr have been measured as a function of bombarding energy over the range 0.84–4.00 MeV, and from the reactions 54Fe(p, γ)55Co and 54Fe(p, p′γ)54Fe over the range 1.05–3.69 MeV. All γ-ray yields were lower by factors of order of 2 than those predicted by statistical model calculations based on global parameter sets. Data are taken from the literature for proton induced reactions on 48Ca, 50Ti, and 51V, which like 52Cr and 54Fe contain a closed shell of 28 neutrons, and for which statistical model calculations were also high by factors of order of 2 or more. A new prescription for obtaining the imaginary well depth for the proton channel is proposed for N = 28 nuclei and it is shown to result in a striking improvement in the agreement between experimental and calculated cross sections. Thermonuclear reaction rates for the (p, γ) reactions on 52Cr and 54Fe are calculated for the temperature range (0.6−10) × 109 K.
    No preview · Article · Jun 1981 · Nuclear Physics A
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    M. R. Anderson · S. R. Kennett · M. E. Sevior · D. G. Sargood
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    ABSTRACT: Cross sections for inelastic scattering of protons by 45SC have been measured over the energy range Ep = 1?2-2? 5 MeV for protons leading to the second, third, fourth, sixth and eighth excited states of 45SC. Statistical model calculations are' in good agreement with the data. Further statistical model cross section calculations are used in an investigation of the part played by inelastic and superelastic scattering of protons in bringing about a thermal distribution of states in 45SCin a stellar interior under the conditions of explosive silicon burning. This mechanism is found to be effective for temperatures above 4? ?x 109 K
    Preview · Article · Jan 1981 · Australian Journal of Physics
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    HJ Gardner · LW Mitchell · SR Kennett · MR Anderson · DG Sargood
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    ABSTRACT: Cross sections have been measured for the reactions 53Cr(p, y)5 4Mn, 53Cr(p, n)53Mn and 53Cr(p, p/)53Cr over the proton energy range O'88-2'40 MeV. The results are compared with the predictions of statistical model, calculations with global optical model parameters, with particular reference to the role of isobaric analogue resonances. Satisfactory agreement between theory and experiment is achieved for all three reactions.
    Preview · Article · Jan 1981 · Australian Journal of Physics
  • M. R. Anderson · S. R. Kennett · L. W. Mitchell · D. G. Sargood
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    ABSTRACT: The strengths of resonances in 25Mg(p, gamma)26Al in the energy range Ep = 317-591 keV have been obtained. Resonance strengths at Ep = 317, 387, 433 and 591 keV have been measured absolutely. The strengths of resonances at Ep = 591 and 433 keV were also deduced by comparison with the strength of the resonance at Ep = 620 keV in 30Si(p, gamma)31P. Relative measurements of 10 resonances in the range Ep = 317-591 keV were made. A search for (p, gamma) strengths below Ep = 300 keV was undertaken and an upper limit for the sum of all possible strengths is given. Thermonuclear reaction rates are calculated for the reaction 25Mg(p, gamma)26Al leading to both the ground state and isomeric first excited state of 26Al in the temperature range T = 5 × 107-5 × 108 K and are compared with rates determined from cross sections obtained from statistical-model calculations. The superelastic and inelastic scattering of protons is investigated as a mechanism by which the 26Al nucleus may attain a thermal distribution of excited states and is shown to be ineffective.
    No preview · Article · Nov 1980 · Nuclear Physics A
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    ABSTRACT: The yields of γ-rays from the reactions 50Ti(p, γ)51V and 50Ti(p, p 'γ)50Ti have been measured as a function of bombarding energy over the range 0.73–4.39 MeV and the yield of neutrons from the reaction 50Ti(p, n)50V has been measured from threshold to a bombarding energy of 4.39 MeV. Competition effects were observed in the γ-ray yields from the (p, γ) and (p, pγ) reactions at the threshold of the (p, n) reaction. The observed yields in all channels were lower by factors of order 3 than those predicted by statistical-model calculations based on global optical parameters and the competition observed in the (p, γ) yield at the opening of the neutron channel was approximately one half that predicted by the statistical-model calculations. These failures of the calculations are tentatively attributed to the neutron closed-shell nature of 50Ti. Thermonuclear reaction rates for the (p, γ) and (p, n) reactions are calculated for the temperature range (0.6–5) × 109 K which includes the range of temperatures of interest in nucleosynthesis calculations.
    No preview · Article · Sep 1980 · Nuclear Physics A
  • S.R. Kennett · M.R. Anderson · Z.E. Switkowski · D.G. Sargood
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    ABSTRACT: The yield of γ-rays from the reaction 49Ti(p, γ)50V has been measured as a function of bombarding energy over the range 0.74–2.27 MeV and the yield of neutrons from the reaction 49Ti(p, n)49V has been measured from threshold to a bombarding energy of 3.25 MeV. Strong competition effects were observed in the γ-ray yield at the opening of the neutron channel. The energy dependence of these cross sections is compared with statistical-model calculations, and good agreement is achieved. Thermonuclear reaction rates are calculated for the temperature range 5 × 108–5 × 109 K which includes the range of temperatures of interest in nucleosysnthesis calculations. The effect of a strong isobaric analogue resonance on the (p, γ) thermonuclear reaction rate is identified and its importance is discussed.
    No preview · Article · Aug 1980 · Nuclear Physics A
  • M.R. Anderson · S.R. Kennett · Z.E. Switkowski · D.G. Sargood
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    ABSTRACT: The yield of 1.332 MeV γ-rays from the reaction 56Fe(α, γ)60Ni has been measured as a function of α-particle bombarding energy in the range 4.2–7.1 MeV. This energy region includes the (α, n) threshold at Eα = 5.46 MeV. The energy dependence of this γ-ray cross section, as well as the (α, nγ) cross section, is compared with statistical model calculations. Good agreement is achieved between these data and calculations using global optical model parameters to determine the transmission functions. In particular, the pronounced threshold effect in the (α, γ) yield, at the opening of the (α, n) channel, is well represented.
    No preview · Article · Apr 1979 · Nuclear Physics A