Elsevier

Nuclear Physics A

Volume 172, Issue 3, 13 September 1971, Pages 513-554
Nuclear Physics A

Off-mass-shell effects and nuclear structure in the 6Li(α, 2α)d reaction

https://doi.org/10.1016/0375-9474(71)90042-XGet rights and content

Abstract

The 6Li(α, 2α)d reaction was studied at 50.4, 59.0, 60.5, 70.3 and 79.6 MeV bombarding energy. For each bombarding energy, several coincident energy spectra of the two emitted α-particles were measured. Special emphasis was placed on measuring spectra at pairs of angles where zero laboratory momentum was possible for the residual deuteron. The spectra were analyzed with the plane wave impulse approximation. From those points in the spectra which corresponded to zero deuteron momentum, off-mass-shell α-α cross sections were extracted. These were found to be in excellent agreement with free α-α cross sections, if free cross sections for the final state α-α c.m. energy were chosen for the comparison. Off-mass-shell α-α cross sections were also extracted for data where the residual deuteron had a momentum of 30 MeV/c. These cross sections were also found to agree with free α-α scattering, but it was necessary to introduce an ad hoc shift in the α-α scattering angle to produce this agreement. Predictions of off-mass-shell α-α cross sections were made using a potential model. These indicate that the off-mass-shell cross section should indeed be very similar to the on-mass-shell cross section at the final state energy.

Using the plane wave impulse approximation a momentum distribution for α-particles in 6Li was extracted from the experimental data. A cluster model for 6Li was devised to fit the binding energy and rms charge radius of 6Li, as well as the 3S1 α-d scattering phase shifts. For comparison with the experimental data, the momentum wave function of the α-particle in 6Li was calculated by taking the Fourier transform of the α-d relative motion. The theoretical and experimental momentum distributions were found to be in serious disagreement, both in magnitude and width at half maximum. By introducing a cut-off radius into the theoretical wave function, the discrepancies between theory and experiment were accounted for. It was also found, that if the cut-off radius is used as an adjustable parameter, then this 6Li wave function and reaction model explains the magnitudes and widths of the α-d relative momentum distri butions determined from a wide variety of other reactions.

References (40)

  • I.S. ShapiroI.S. Shapiro
  • I.V. Kurdyumov et al.

    Phys. Lett.

    (1970)
  • M. Jain

    Nucl. Phys.

    (1970)
  • Y.C. Tang
  • M.J. Moravcsik

    Nucl. Phys.

    (1958)
  • R. R. Whitney and M. R. Yearian, private...
  • D. F. Jackson, in Advances in nuclear physics, vol. 4, eds. M. Baranger and E. Vogt (Plenum, New York) to be...
  • D.W. Devins

    Rev. Mod. Phys.

    (1965)
  • R.L. Burman et al.

    Phys. Rev. Lett.

    (1968)
  • S. Ali et al.

    Nuovo Cim.

    (1967)
  • D.R. Thompson et al.

    Phys. Rev.

    (1969)
  • B. Gottschalk et al.

    Phys. Rev.

    (1907)
  • R. Adkins et al.

    Phys. Rev.

    (1955)
    W.T. Pinston et al.

    Phys. Rev.

    (1958)
    F.C. Barker

    Nucl. Phys.

    (1966)
  • P. DarriulatP. Darriulat

    Phys. Rev.

    (1965)
  • J.W. Watson
  • H.G. Pugh

    Phys. Rev. Lett.

    (1969)
  • A.D. Bacher

    Bull. Am. Phys. Soc.

    (1969)
  • J.R. Pizzi

    Nucl. Phys.

    (1969)
  • P.G. Roos

    Phys. Rev. Lett.

    (1969)
  • D.I. Bonbright
  • Cited by (65)

    View all citing articles on Scopus
    †††

    Research supported in part by the US Atomic Energy Commission.

    Now at University of Manitoba, Winnipeg, Manitoba, Canada.

    ††

    Now at Cyclotron Branch, Nuclear Physics Division, Naval Research Laboratory, Washington, D.C.

    View full text