DETERMINATION OF THE MULTIPOLARITY OF NUCLEAR ELECTROMAGNETIC TRANSITIONS USING A MAGNETIC PAIR SPECTROMETER

Journal Article · Mon Jan 13 04:00:00 EST 1964 · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D

OSTI ID:4122412

Warburton, E K; Alburger, D E; Gallman, A; Wagner, P; Chase, Jr, L F

An intermediate-image magnetic pair spectrometer was modified so as to respond to positron-electron internal pairs emitted at large relative angles thereby making the pair-line transmission depend sensitively on the multipolarity of electromagnetic transitions above 2 Mev. The modification consists of a specially designed spiral baffle system that selects pnirs emitted within 105 deg azimuthal sectors on opposite sides of the axis. Measurements are made of the net yield of an internal-pair-conversion coincidence line, both in the normal spectrometer operation and with the spiral baffle instalied, giving a reduction ratio R /sub omega / = Y/sub with baffle//Y/sub without baffle/. Experimental ratios were determined for 14 known transitions including E0, E1, M1, E2, M2, and E3 multipoles between 3 and 7 Mev. Theoretical calculations were carried out on the spectrometer transmission, when using the baffle, for E0, E1 through E4, and M1 through M4 transitions from nonaligned nuclei over a wide energy range. These transmissions were combined with previous calculations of the transmission without the baffle in order to derive curves of R/sub omega /(l) versus transition energy for the various multipoles. A best fit to the experimental ratios for the known multipoles was made in the calculations by adjusting slightly the values of the mean spectrometer-entrance angle and the sector angle omega of the baffle. The various ratio curves thus obtained are spaced widely enough apart to allow clear multipole assignments to be made in most cases. For mixed transitions from aligned nuclei, calculations were made of correction factors to be applied to the experimentally determined ratios. It is shown how the correction factors can be derived from separate measurements of the angular distributions of the corresponding gamma rays. The method was applied to a number of previously unassigned transitions in Be/sup 10/, B/sup 10/, C/sup 14, and N/sup 14/ leading to new spin and parity information on certain levels in these nuclei. In particular, it is found that the Be/sup 10/ 6.18-Mev level and the C/sup 11/ 6.58-Mev level are both 0/sup +/ and the N/sup 14/ 5.10-Mev level has odd parity. (auth)

• Research Organization: Brookhaven National Lab., Upton, N.Y.
• NSA Number: NSA-18-006238
• OSTI ID: 4122412
• Report Number(s): BNL-7188; 0031-899X
• Journal Information: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Journal Name: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D Vol. Vol: 133; ISSN PHRVA
• Country of Publication: United States
• Language: English

Related Subjects

ABSORPTION
ANGULAR DISTRIBUTION
BERYLLIUM 10
BORON 10
CARBON 14
COINCIDENCE METHODS
ELECTRIC CHARGES
ELECTRONS
GAMMA RADIATION
INTERNAL CONVERSION
MAGNETIC FIELDS
MAGNETIC MOMENTS
MEASURED VALUES
MULTIPOLES
NITROGEN 14
NUCLEAR MODELS
NUCLEI
NUMERICALS
PAIR PRODUCTION
PARITY
PHYSICS
PLATES
POSITRONS
SPECTROMETERS
SPIN
TRANSIENTS