(Li6,t) reaction on medium-mass nuclei and the mass and spectrum of

Abstract

The ( Li, t) reaction was studied with a 34-MeV Li beam on enriched targets of "Mg, "Si, "Fe, 6Fe, and "Ni. The tritons were momentum analyzed in a quadrupole-dipole-dipole-dipole magnetic spectrograph and detected with a 1-m helical cathode proportional counter that covered about 4 MeV of excitation. Cross sections for the ( Li, t) reaction to strongly excited states are generally in the range of 1 to 10 It(,b/sr with exceptions up to 50 p,b/sr, Comparisons are made, where possible, between the selectivity of this reaction and other reactions leading to the same final nuclei, A similarity with single-neutron stripping is observed, which suggests a ( Li, t) reaction mechanism involving direct transfer of a proton-pair coupled to a single neutron. The possible two-step process { Li, d){d,t) is also suggested to account for two cases of f», hole states populated in the nickel isotopes. The "Ni( Li, t) 'Zn Q value was measured to be -4736+23 keV giving a mass excess of -56352+26 keV for 'Zn, This mass excess is believed to be more reliable than previous measurements with other techniques that differ by 500 keV. The triton spectrum for the 'SNi( Li, t} 'Zn reaction yields the first measurement of the energy levels of 'Zn, NUCLEAR HEACTrONS "Mg('Li, t~, 28Si('Li, t), "Fe('Li, t), '~re(6Li, t~, ¹(6I, i, t ), E(;L; --34 MeV; enriched targets, Q3D spectrograph, measured do/dQ, Et, energy levels~YSi,~'S,~7Ni, 5~Ii, 6'Zn; mass 6iZn; reaction mechanism discussed, correspondence with single-neutron transfer noted.

Study of ($^6$Li, $d$) and ($^6$Li, $t$) reactions on $^{22}$Ne and implications for $s$-process nucleosynthesis

“…A few potential direct reaction mechanisms were proposed in the earlier ( 6 Li,t) studies. One is that the proton pair goes into the lowest accessible orbits, while the odd neutron is transferred into single-particle states (in the present experiment, this would populate a similar set of 25 Mg states as 24 Mg(d, p) 25 Mg) [71]. Another possibility is that one proton is transferred to the lowestavailable orbital and the remaining proton-neutron pair is transferred as in the (α,d) reaction (analogous to 23 Na(α, d) 25 Mg in the present case) [65].…”

“…Another possibility is that one proton is transferred to the lowestavailable orbital and the remaining proton-neutron pair is transferred as in the (α,d) reaction (analogous to 23 Na(α, d) 25 Mg in the present case) [65]. Finally, an analogous mechanism to direct (α, n) reactions with transfer of a 3 He cluster ( 22 Ne(α, n) 25 Mg at present) has also been proposed [71]. However, the reaction's selectivity in populating the specific levels observed in the past experiments [64,65,67,70,71] are not universally explained by any of the above mechanisms.…”

“…To date, there are no published data on the 22 Ne( 6 Li,t) 25 Mg reaction and hence this represents the first analysis of states in 25 Mg populated through this reaction mechanism. However, the ( 6 Li,t) reaction mechanism has been studied on a variety of light-to-medium mass targets including 13 C [64-66], 16 O [67-69], 24 Mg, 28 Si, 40 Ca, 54,56 Fe, and 58 Ni [70,71], as a potential method for spectroscopy. Most of these studies were carried out in the 1970s or earlier except for the recent 13 C( 6 Li,t) study of Ref.…”

β+decay of61Ga

“…This paper reports on a new measurement of the mirror β + -decay of the 61 Ga nucleus (Z=31, N=30). Excited levels of the daughter nucleus 61 Zn are well known from reaction studies [17,18] and in-beam spectroscopy experiments [19,20,21,22]. The half-life of 61 Ga, produced in fragmentation reactions, was measured with 20% accuracy by Winger et al [23].…”

Ελαστική σκέδαση και μηχανισμοί αντιδράσεων κοντά στο φράγμα Coulomb για το σύστημα 7Be+28Si

“…Si( 7 Be,4 He)31 S reaction are more erratic, since there are no suitable spectroscopic factors available in the literature for the 31 S | 28 Si + 3 He overlaps. The only experimental indication for population of states in 31 S comes from a measurement of the 28 Si( 6 Li, 3 H)31 S reaction[197]. Here the 0.0 MeV 1/2 + , 1.25 MeV 3/2 + , and 4.45 MeV 7/2 − states were the main states observed in 31 S. The Q-matching conditions for this reaction favor the population of highly exited states (E exc > 10 MeV) close to or above the 3 He emission threshold.…”