Isotopic-Spin Selection Rule Violation in the $B^{10} (d, α) {Be}^{8}$ Reaction

1 August 1961

journal article
research article
Published by American Physical Society (APS) in Physical Review B

Vol. 123 (3), 958-967
https://doi.org/10.1103/physrev.123.958

Abstract

All previous tests of the isotopic-spin selection rule in (

d, α

) reactions were obscured by statistical weight factors because in each case the initial and final nuclear states had spin and parity

0^{+}

. The

B^{10} (d, α) {Be}^{8}

reaction provides a test of the isotopic-spin selection rule free from this restriction. The energy levels of

{Be}^{8}

near the lowest

T = 1

level were studied with the

{Li}^{6} ({He}^{3}, p) {Be}^{8}

and

{Be}^{9} ({He}^{3}, α) {Be}^{8}

reactions as well as with the

B^{10} (d, α) {Be}^{8}

reaction. Energy levels in

{Be}^{8}

were found at 16.623±0.010 Mev, 16.921±0.010 Mev, and 17.637±0.006 Mev. The widths are 95±20 kev, 85±20 kev, and <15 kev, respectively. The first of these levels is the lowest

T = 1

state, whereas the second is

T = 0

and the third probably

T = 1

. Energy levels at 16.08 Mev and a

J = 2

level at 17.7 Mev, reported by other laboratories, were not observed. The ratio of the differential cross sections for formation of the 16.62- and 16.92-Mev levels was measured over a range of angles and bombarding energies. The ratio is about 1.4 and is roughly constant for both the

{Li}^{6} ({He}^{3}, p) {Be}^{8}

and

B^{10} (d, α) {Be}^{8}

reactions. This implies complete violation of the selection rule because the latter reaction should not go to the

T = 1

level. Arguments are given which indicate that the

T = 0

impurities in the 16.62-Mev

T = 1

level are probably quite small. Consequently, the failure of the selection rule probably results from the complete intermixing of

T = 0

and

T = 1

states in the

C^{12}

compound nucleus near 28-Mev excitation. Groups from the

C^{12} ({He}^{3}, p) N^{14}

reaction were seen corresponding to levels in

Keywords

This publication has 15 references indexed in Scilit:

Comparison ofPo210Alpha-Particle Energy with theLi7(p, n)Be7Reaction Threshold Energy
Physical Review B, 1960
$ft$ Value of $O^{14}$ and the Universal Fermi Interaction
Physical Review Letters, 1960
Violation of the Isotopic Spin Selection Rule in theCa40(d, α)K38Reaction
Physical Review B, 1959
Energy levels of light nuclei. VI
Nuclear Physics, 1959
${Si}^{28} (d, α) {Al}^{26}$ Reaction
Physical Review B, 1959
Nuclear Levels in $P^{30}$ , $S^{33}$ , and $S^{35}$
Physical Review B, 1958
Excited States in ${Be}^{7}$ and ${Be}^{8}$
Physical Review B, 1957
Isotopic-Spin Selection Rule Violation in the $O^{16} (d, α) N^{14}$ Reaction
Physical Review B, 1956
The 12 C(γ, 3α) reaction energy levels of 8 Be and 12 C
Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1955
Conservation of Isotopic Spin in Nuclear Reactions
Physical Review B, 1952

Cited by 53 articles

Isotopic-Spin Selection Rule Violation in theB10(d, α)Be8Reaction

Abstract

Keywords

Isotopic-Spin Selection Rule Violation in the $B^{10} (d, α) {Be}^{8}$ Reaction