ANGULAR DISTRIBUTIONS OF ALPHA PARTICLES AND PROTONS FROM THE REACTIONS N$sup 14$(/cap alpha/,/cap alpha/)N$sup 14$ Na$sup 23$(/cap alpha/,p)Mg$sup 26$, Al$sup 27$(/cap alpha/,p)Si$sup 30$ AND Si$sup 28$(/cap alpha/,p)p$sup 31$ AT 19 Mev

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1961

OSTI ID:4791787

Ploughe, W D

A focused and energy-analyzed 19-Mev alpha-particle beam is used to bombard the targets. The elastically and inelastically scattered alpha particles from the gaseous N/sup 14/ target are detected by means of nuclear photographic plates spaced every 2.5 deg in a multiplate scattering chamber covering the laboratory angular range of 10 to 170 deg . The reaction protons from the Na/sup 23/, Al/sup 27/, and Si/sup 28/ targets are detected in a CsI (Tl) scintillation spectrometer and recorded in a twenty-channel pulse-height analyzer. The protons are identified by absorbing or degrading the energy of all shorter-range reaction products before they strike the CsI (Tl) crystal. The elastic angular distributions of alpha particles from N/sup 14/ exhibit a diffraction-like pattern, similar to that observed on other light nuclei, in the forward direction, but this pattern becomes smeared out in the backward direction. The cross section deviates strongly from pure Coulomb scattering, rising more than a factor of 225 above the Rutherford cross section in the backward direction. The forward part of the elastic angular distribution is fitted with a diffraction model using an interaction radius of 5.89 x 10/sup 13/ cm. The angular distribution for the Q = -3.95 Mev group is fitted using an interaction radius of 5.9 x 10/sup -13/ cm. With the same interaction radius, a best fit to the data for the unresolved Q = -4.91 and --5.10 Mev doublets is obtained. This best fit by odd-order spherical Bessel functions is consistent with the assignment of negative parity to both the 4.91- and 5.10-Mev levels. The proton angular distributions for all three targets exhibit diffraction-like patterns and are peaked in the forward direction. Assuming that the reaction proceeds by the knockout process, the angular distributions are fitted to several models. From the normalizing constant a factor is extracted, which contains nuclear information concerning the interaction potential and the reduced widths. The angular distributions are also integrated to give total cross sections. For the Si/sup 28/ reaction an incoherent heavy-particle stripping term is added to the cross section for the knockout process to obtain better fits at large angles. The cross sections to the ground states of the final nuclei increase through the series F/sup 19/, Na/sup 23/, and Al/sup 27. The large cross section to the P/ sup 31/ ground state can be interpreted as the knockout of an s/sub 1/2/ proton from Si/sup 28/, in contrast to the usual picture of a d/sub 5/2/ closed shell of Si/sup 28/ and the capture of an 1 = 0 alpha particle or as the capture of an 1 = 0 triton in an alpha-particle stripping process. Comparison of the total cross sections shows that the sodium-minus-proton core in the Na/sup 23/( alpha ,p)Mg/ sup 26/ is more common to the first excited state of Mg/sup 26/ than to the ground state. In the case of the on to the ground state, as is the case in the Si/sup 28/( alpha ,p)P/sup 31/ reaction. (Dissertation Abstr., 22: No. 7, 1962.)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-17-000876
• OSTI ID: 4791787
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ALPHA PARTICLES
ALUMINUM 27
ANGULAR DISTRIBUTION
CESIUM IODIDES
CROSS SECTIONS
MAGNESIUM 26
NITROGEN 14
NUCLEAR REACTIONS
PHOSPHORUS 31
PHOTOGRAPHIC FILM DETECTORS
PHYSICS
PROTONS
SCATTERING
SCINTILLATIONS
SILICON 28
SILICON 30
SODIUM 24
SPECTROMETERS
TARGETS