G.E. Moore

Structure of 14C from 12C(t, p)

Abstract The reaction 12 C(t, p) 14 C has been investigated with an 18 MeV triton beam. Twenty energy levels of 14 C were identified up to 13 MeV excitation. Angular distributions were measured and compared with DWBA calculations. A previously unreported 0 + level at 9.75 MeV was observed; it undoubtedly corresponds to the second predominantly sd shell 0 + state in 14 C. Additional spin and parity assignments have been made in the present work: 9.81 MeV, (1 − ); 10.43 MeV, 2 + ; 10.50 MeV, (3 − ); 10.74 MeV, 4 + ; 11.40 MeV, 1 − ; 11.67 MeV, (1 − ); 11.73 MeV, (5 − ); 12.58 MeV, (2 + , 3 − ); 12.87 MeV. 2 + , 3 − ; and 12.96 MeV, (1 − ); none of which had a definite spin and parity assignment previously. Our results confirm the previous information on the level structure of 14 C below 8.5 MeV. The cross section for the unnatural parity state at 7.34 MeV, J π = 2 − , is well reproduced by a two-step reaction calculation. The results are compared with the predictions of a weak coupling model.

Spectroscopy of 16C

Abstract The 14C(t, p)16C reaction locates five new states in 16C, at excitation energies of 3120 ± 15, 3983 ± 10, 4136 ± 10 and 6109 ± 15 keV, in addition to the g.s. and 1.76 MeV states. The 3.02 and 3.98 MeV states appear to be the second 0+ and 2+ 2p-2h states, respectively. The 4.14 MeV state has Jπ = 4+ and the 6.11 MeV state has Jπ = 2+, 3−, or 4+.

Study of 78As with the 80Se(d, α) reaction

Abstract The 80 Se(d, α) 78 As reaction was investigated with 16.0 MeV deuterons. The ground state and nineteen excited levels of 78 As were identified up to 1.27 MeV excitation energy. Except for the level at 276 keV, all the other excited levels were previously unreported. Angular distributions were measured and compared with DWBA calculations. Unambiguous L -values could be extracted for nine transitions. The transition to the ground state of 78 As has an L = 3 character. Four levels at 276, 536, 967 and 1072 keV were tentatively assigned as J π = (1 + ) levels. Four transitions were observed to proceed with L = 1 transfer, indicating a significant shift from the shell model description in this mass region. The configuration dependence on angular-distribution shape was examined. The measured Q -value for the 80 Se(d, α) 78 As reaction is 5.755 ± 0.012 MeV.

Spectroscopic information from the /sup 9/Be(/sup 7/Li,/sup 6/He)/sup 10/B and /sup 9/Be(/sup 7/Li,/sup 6/Li)/sup 10/Be reactions

Elastic scattering of /sup 7/Li + /sup 9/Be and /sup 6/Li + /sup 10/B has been measured at E (/sup 7/Li) = 34 MeV and E (/sup 6/Li) = 30 MeV and the data have been described with the standard optical model. Both /sup 9/Be(/sup 7/Li,/sup 6/He) and /sup 9/Be(/sup 7/Li,/sup 6/Li) reaction data were measured. Extreme forward angle (/sup 7/Li,/sup 6/He) data were taken so that the j transfer (3/2 or 1/2) to the first two 1/sup +/ states in /sup 10/B could be determined. Both states were found to be populated predominantly by p/sub 1///sub 2/ transfers. The absolute spectroscopic factors obtained are in good agreement with 35 MeV (/sup 3/He,d) data, but not with 17 MeV data. Comparisons between the spectroscopic factors obtained from the (d,n), (/sup 3/He,d), and (/sup 7/Li,/sup 6/He) reactions shows a clear need for the energy dependence of these reactions to be understood before reliable absolute spectroscopic factors for /sup 10/B can be obtained. The (/sup 7/Li,/sup 6/Li) results were in good agreement with the calculations of Cohen and Kurath, in contrast to the (/sup 7/Li,/sup 6/He) results.

2p-1h states in 17N☆

Abstract States populated in the 15 N(t,p) 17 N reaction at 15 MeV are compared with those in the 16 O(t,p) 18 O reaction at the same energy. On the basis of this comparison several spins and parities are assigned. Cross-section ratios are in rough agreement with a weak-coupling model.

Spins of states near 10 MeV excitation in 14C

In the 12C(t,p)14C reaction a previously unreported state is observed at Ex=9.75 MeV and is assigned Jpi =0+. Other Jpi assignments are 9.81 MeV, (1-); 10.43 MeV, 2+; 10.50 MeV, (3-); and 10.74 MeV, 4+.

/sup 12/C + /sup 14/N reaction at E/sub lab/ = 53 MeV

Angular distributions have been measured for the reactions /sup 12/C(/sup 14/N, /sup 9/Be)/sup 17/F, /sup 12/C(/sup 14/N, /sup 10/B)/sup 16/O, and /sup 12/C(/sup 14/N, /sup 12/C)/sup 14/N at E14/sub N/ = 53 MeV and compared to Hauser-Feshbach predictions. Additionally, excitation functions for /sup 12/C(/sup 14/N, /sup 6/Li)/sup 20/Ne and /sup 12/C(/sup 14/N, /sup 10/B)/sup 16/O in the region of 53 MeV have been taken. The reactions which involve /sup 9/Be and /sup 10/B are well fitted by the Hauser-Feshbach theory, indicating these products are formed via a compound nuclear reaction. The relative cross sections between the discrete states populated in /sup 9/Be + /sup 17/F and /sup 10/B + /sup 16/O are best described by a critical angular momentum between 14 and 15 h. The magnitude of the /sup 12/C(/sup 14/N, /sup 12/C)/sup 14/N reaction is poorly described by Hauser-Feshbach theory, indicating a noncompound nature for this reaction channel. (AIP)

l determinations for 12C + 12C☆

Abstract Detailed angular-distribution measurements and Legendre-polynomial fits for 12 C ( 12 C , α 0 ) 20 Ne ( g.s ) in the bombardi energy region of the so-called “12 + ” bump in 12 C + 12 C inelastic scattering show conclusively that l = 10 dominates the α 0 exit channel throughout the range, except near the narrow 12 + resonance that was previously known.