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Title: Observation of a new transition in the {beta}-delayed neutron decay of {sup 18}N

Abstract

A new transition is reported in the beta-delayed neutron decay of {sup 18}N. The observed neutron energy is 3.78{+-}0.05 MeV with a branching ratio of 0.05{+-}0.03%, which corresponds to an excitation energy of 12.05{+-}0.05 MeV in the daughter nucleus {sup 18}O. The log ft value of this transition is 5.24{+-}0.3, which, together with the previously reported electron scattering data, determines the J{sup {pi}} value of this level to be 1{sup -}. The experimental data are compared to the shell model calculations in different model spaces.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;  [1]; ; ;  [2]
  1. School of Physics and MOE Key Laboratory of Heavy Ion Physics, Peking University, Beijing 100871 (China)
  2. Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China) (and others)
Publication Date:
OSTI Identifier:
20995341
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevC.75.057302; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; BETA-DELAYED NEUTRONS; BRANCHING RATIO; DECAY; DELAYED NEUTRONS; ELECTRONS; EXCITATION; FT VALUE; MEV RANGE 10-100; NITROGEN 18; OXYGEN 18; SCATTERING; SHELL MODELS

Citation Formats

Lou, J. L., Li, Z. H., Ye, Y. L., Hua, H., Jiang, D. X., Lv, L. H., Kong, Z., Zhang, Y. M., Xu, F. R., Zheng, T., Li, X. Q., Ge, Y. C., Wu, C., Zhang, G. L., Chen, Z. Q., Li, C., Pang, D. Y., Xu, H. S., Sun, Z. Y., and Duan, L. M. Observation of a new transition in the {beta}-delayed neutron decay of {sup 18}N. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.057302.
Lou, J. L., Li, Z. H., Ye, Y. L., Hua, H., Jiang, D. X., Lv, L. H., Kong, Z., Zhang, Y. M., Xu, F. R., Zheng, T., Li, X. Q., Ge, Y. C., Wu, C., Zhang, G. L., Chen, Z. Q., Li, C., Pang, D. Y., Xu, H. S., Sun, Z. Y., & Duan, L. M. Observation of a new transition in the {beta}-delayed neutron decay of {sup 18}N. United States. doi:10.1103/PHYSREVC.75.057302.
Lou, J. L., Li, Z. H., Ye, Y. L., Hua, H., Jiang, D. X., Lv, L. H., Kong, Z., Zhang, Y. M., Xu, F. R., Zheng, T., Li, X. Q., Ge, Y. C., Wu, C., Zhang, G. L., Chen, Z. Q., Li, C., Pang, D. Y., Xu, H. S., Sun, Z. Y., and Duan, L. M. Tue . "Observation of a new transition in the {beta}-delayed neutron decay of {sup 18}N". United States. doi:10.1103/PHYSREVC.75.057302.
@article{osti_20995341,
title = {Observation of a new transition in the {beta}-delayed neutron decay of {sup 18}N},
author = {Lou, J. L. and Li, Z. H. and Ye, Y. L. and Hua, H. and Jiang, D. X. and Lv, L. H. and Kong, Z. and Zhang, Y. M. and Xu, F. R. and Zheng, T. and Li, X. Q. and Ge, Y. C. and Wu, C. and Zhang, G. L. and Chen, Z. Q. and Li, C. and Pang, D. Y. and Xu, H. S. and Sun, Z. Y. and Duan, L. M.},
abstractNote = {A new transition is reported in the beta-delayed neutron decay of {sup 18}N. The observed neutron energy is 3.78{+-}0.05 MeV with a branching ratio of 0.05{+-}0.03%, which corresponds to an excitation energy of 12.05{+-}0.05 MeV in the daughter nucleus {sup 18}O. The log ft value of this transition is 5.24{+-}0.3, which, together with the previously reported electron scattering data, determines the J{sup {pi}} value of this level to be 1{sup -}. The experimental data are compared to the shell model calculations in different model spaces.},
doi = {10.1103/PHYSREVC.75.057302},
journal = {Physical Review. C, Nuclear Physics},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • The [beta]-delayed neutron decay of [sup 18]N has been studied using a time-of-flight array with high efficiency. The [sup 18]N ions were produced by fragmentation of a [ital E]/[ital A]=75 MeV [sup 22]Ne beam. Transitions to nine neutron unbound states have been observed with a total branching ratio of 2.2[plus minus]0.4%. The results are compared with measurements of the decay to [gamma]- and [alpha]-emitting states and the differences between the present results and a recent measurement of the [ital P][sub [ital n]] value are discussed.
  • The {Beta}-delayed neutron decay of {sup 17}C and {sup 18}C has bear measured to investigate neutron-unbound levels in {sup 17}N and {sup 19}N. Levels of interest in {sup 17}N and {sup 18}N are those near the neutron threshold which may play a role in a astrophysical reprocess during an inhomogeneous Big Bang. Radioactive ion beaming of {sup 17}C and {sup 18}C were produced by beam fragmentation at the NSCL MSU. Ions were implanted in a plastic scintillator which served as a start detector for a time-of-flight measurement. Neutrons were detected in the MSU neutron detector array. Several neutron groups havemore » been observed and the results will be discussed.« less
  • The results of the first spectroscopic studies of delayed neutron and {gamma} emission following the {beta} decay of {sup 19}N and {sup 20}N are reported. Nuclides were produced by fragmenting an 80 MeV/nucleon {sup 22}Ne beam in a 546 mg/cm{sup 2} thick Be target and were separated at high velocities with the A1200 fragment separator. The nuclides were implanted in a thin plastic scintillator at the center of an array of neutron scintillators to determine the neutron time-of-flight spectrum. Two hyperpure germanium detectors were used to observe coincident {gamma} events. The {beta}-{gamma},{beta}-n, and {beta}-n-{gamma} coincidence spectra were analyzed to obtainmore » the energies of the states populated in {sup 18}O, {sup 19}O, and {sup 20}O following the {beta} decay. Eight new neutron energies with a total neutron emission probability of 41.8(9)%, six {gamma} transitions among the excited states of {sup 19}O, and four {gamma} transitions among the excited states of {sup 18}O were identified in the {sup 19}N {beta} decay. Seven new neutron energies with a total neutron emission probability of 42.9(14)%, ten {gamma} transitions among the excited states of {sup 20}O, and two {gamma} transitions among the exited states of {sup 19}O were observed from the {sup 20}N {beta} decay. Half-lives of 336(3) and 136(3) ms were determined for the {sup 19}N and {sup 20}N decays, respectively. The branching ratios of both decays were deduced and compared with USD (universal sd-shell) shell model calculations. The {beta} decay schemes for {sup 19}N and {sup 20}N were de0011duc.« less
  • The first spectroscopic study for the {beta} decay of {sup 21}N is carried out based on {beta}-n, {beta}-{gamma}, and {beta}-n-{gamma} coincidence measurements. The neutron-rich {sup 21}N nuclei are produced by the fragmentation of the E/A=68.8 MeV {sup 26}Mg primary beam on a thick {sup 9}Be target and are implanted into a thin plastic scintillator that also plays the role of {beta} detector. The time of flight of the emitted neutrons following the {beta} decay are measured by the surrounding neutron sphere and neutron wall arrays. In addition, four clover germanium detectors are used to detect the {beta}-delayed {gamma} rays. Thirteenmore » new {beta}-delayed neutron groups are observed with a total branching ratio of 90.5{+-}4.2%. The half-life for the {beta} decay of {sup 21}N is determined to be 82.9{+-}7.5 ms. The level scheme of {sup 21}O is deduced up to about 9 MeV excitation energy. The experimental results for the {beta} decay of {sup 21}N are compared to the shell-model calculations.« less
  • The {beta}-decay of {sup 18}N has been studied using {beta}-n and {beta}-{gamma} coincidence methods. The {sup 18}N ions were produced by the fragmentation of the E/A=68.8 MeV {sup 22}Ne beam on a thick beryllium target. A newly constructed neutron detector system with wide energy detection range and low-energy detection threshold was used. The 619 {+-} 2 ms half-life of the {sup 18}N {beta}-decay was found to be in very good agreement with the previous measurements. Transitions to 11 {beta}-delayed neutron emitting states in {sup 18}O have been observed with a total branching ratio of 6.98 {+-} 1.46%. The Gamow-Teller {beta}-decaymore » strengths of {sup 18}N to these levels were deduced and compared with the shell model calculations. The intensities of the strong {gamma}-ray transitions in {sup 18}O were found to be consistent with recent work.« less