Selective Population and Neutron Decay of the First Excited State of Semi-Magic 23O

We have observed an excited state in the neutron-rich semi-magic nucleus 23O for the first time. No such states have been found in previous searches using y-ray spectroscopy. The observation of a resonance in n-fragment coincidence measurements confirms the speculation in the literature that the lowest excited state is neutron unbound and establishes positive evidence for a 2.8(1) MeV excitation energy of the first excited state in 23O. The non-observation of a predicted second excited state is explained assuming selectivity of inner-shell knockout reactions

Final state interaction or a 3H excited state?

An inclusive a-particle spectrum from the 1H(6He,a) reaction has been measured at a 6He laboratory energy of 23.9 MeV. A resonancelike structure is observed at an a-particle lab energy of about 20 MeV, which corresponds to an energy of End50.6 MeV in the n-d channel. An analysis of the spectrum shows that it cannot be explained by the effect of binary final-state interactions. The hypotheses that this structure represents ~a! a new excited state of tritium or ~b! a three-body final-state interaction are discussed

Evidence for nonequilibrium proton emission in a low-energy heavy-ion reaction

Correlation functions for p-p, p-d, p-α, d-α, and α-α were measured for the 16O+27Al system at a beam energy of 72 MeV. The detector array was centered at laboratory angle of 20°. Compared to published data obtained at larger scattering angles, an unexpected dependence on angle is seen for the p-p channel. The observed anticorrelation is stronger at more forward angles, which suggests that correlation functions are sensitive to the specific reaction mechanisms producing the light-charged particles

Big Physics At Small Places: The Mongol Horde Model Of Undergraduate Research

A model for engaging undergraduates in cutting-edge experimental nuclear physics research at a national user facility is discussed.  Methods to involve students and examples of their success are presented

Radiobiological Evaluation of Immigrants from the Vicinity of Chernobyl

Eighty individuals (55 adults and 25 children) who were residents of four cities (Kiev, Mozyr, Gomel and Bobrujsk) located 100± 200 km from Chernobyl at the time of the accident in 1986 were tested after immigrating to the US from 1989–1991. A whole-body counter was employed to quantitate radiocesium content. In addition, two biological measures of radiation effects, namely, chromosomal integrity using the micronucleus assay and somatic mutation analysis of erythrocytes at the glycophorin A (GPA) locus, were applied to this group. Radiocesium activity in the body ranged from 0 to 56.8 Bq/kg with a mean and standard deviation of 5.0 ± 8.2 and a median value of 2.0 Bq/kg. Mean radiocesium content by groups was highest in adult males (9.0 ± 11.7; range 0.21–56.8 Bq/kg) followed by adult females (3.3 ± 4.5; range 0–2. ́3 Bq/kg), male children (3.0 ± 5.7; range 0–20.2 Bq/kg) and lowest in female children (1.6 ± 3.5; range 0–12.7 Bq/kg). Individuals with the highest radiocesium content in each group belonged to one family that lived in Mozyr (100 km from Chernobyl) until emigrating in 1989. The frequency of lymphocyte micronuclei and erythrocyte GPA allele- loss (é /N) somatic mutations were both significantly correlated with radiocesium content (r=0.57, p=0.002; r=0.75, p=0.002, respectively). The micronucleus frequency also correlated with the estimated internal absorbed dose from radiocesium in a subset of 20 immigrants for whom this calculation was possible (r=0.71, p=0.0005). Altogether, the biomonitoring data indicate that some subjects had radiation doses sufficient to produce gene and chromosomal mutations in blood cells, although these affects cannot be attributed solely to radiocesium exposure

BigPhysics at Small Places: The Mongol Horde Model of Undergraduate Research

A model for engaging undergraduates in cutting-edge experimental nuclearPhysics research at a national user facility is discussed. Methods to involve students and examples of their success are presented