Nuclear structure, nuclear reaction

Thesis



In this thesis, particle- particle angular correlations for reactions in non-zero degree geometry and with non-zero spin nuclei are performed and found to be a valuable tool for spin determination, (d-α) angular correlations in the reaction process ¹⁴N(⁶Li,d)¹⁸F* (α)¹⁴N are measured for three high excited states in ¹⁸F with a ⁶Li beam of 36MeV. Spins and parities for two of the observed states are determined, and in agreement with theoretical predictions, these states are suggested as members of the K^π=1⁺ α-rotational band. The three analysed 9.58MeV 6⁺, 11.2MeV, 14.1MeV 8⁺ states are found to undergo a predominant α-particle decay to the ground state of ¹⁴N. Gamow unbound formalism is carried out for the state descriptions. Angular distributions are measured and analysed under Hauser Feshbach and exact finite range DWBA formalisms. Spectroscopic factors are extracted and compared to shell model predictions, showing a reasonable agreement.

(³He-α) and (t-α) angular correlations for the reaction processes ¹⁴N(⁶Li,³He)¹⁷0* (α)¹³C and ¹⁴N(⁶Li,t)¹⁷F* (α)¹³N respectively are measured at 36MeV of ⁶Li. High selectivity is observed for the three particle transfer processes and percentages of the different particle decays for the high populated states are presented. Structureless angular correlations hinder definite spin and parity assignements, but the displacement of the preferred direction observed in the pattern decay gives some information on the range of plausible angular momenta. Shell model calculations are performed for comparison with the experimental data, and this allows tentative spin identifications. EFR EWEA calculations are carried out, providing some confirmation on the spin suggestions. Useful nuclear structure information is obtained for the mass 17 and 18 nuclear states.

The particle-particle angular correlation expression for a process where a direct reaction mechanism is involved is reviewed, programmed and used for obtaining the theoretical predictions to be compared to the experimental results.

Authors: Etchegoyen, M; Etchegoyen, Maria Cristina Berisso de

• Publication date: 1982
• DOI: 10.5287/ora-xq7w10qdz
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Subjects: Nuclear spin; Angular correlations (Nuclear physics)