Jerome J. Wesolowski

Trace element concentrations in aerosols from the San Francisco Bay Area

Abstract Twenty-nine trace elements in air over the San Francisco Bay Area have been classified into a soil-derived aerosol group, a marine aerosol group, and a third group of elements whose relative concentrations may be significantly altered by anthropogenic pollution sources. The third group includes Se, Zn, Br and Hg. Samples from nine Bay Area monitoring stations were subjected to neutron activation analysis. A statistical correlation analysis was used to group the elements. The elemental abundances from the analysis were compared to calculated abundances based on Fe concentration in the soil group and Na in the ocean group. The analysis was also used to assess whether the locations of specific monitoring stations are representative of their surrounding area.

Lead and bromine particle size distributions in the San Francisco Bay area.

Abstract Lead and bromine particle size distributions have been measured in the San Francisco Bay area. Samples taken with Andersen impactors during a 4-day period were analyzed by X-ray fluorescence and neutron activation analysis. The results, including approximately 50 per cent mass concentration on the afterfilter, nearly constant Br/Pb ratio at all stations, and the good correlation with CO levels, are consistent with the properties of a condensation aerosol from automobiles. No greater loss of Br from the smaller particles was observed, in contradiction to expectations from a diffusion mechanism.

Study of the 22Ne(d, d)22Ne, 22Ne(d, p)23Ne, 22Ne(d, t)21Ne and 22Ne(p, d)21Ne reactions

Abstract The nuclear reactions 22 Ne(d, d) 22 Ne, 22 Ne(d, p) 23 Ne and 22 Ne(d, t) 22 Ne induced with 12.1 MeV deuterons and 22 Ne(p, d) 21 Ne induced with 18.2 MeV protons have been studied by employing a gas target of enriched 22 Ne and beams accelerated in the Livermore variable energy cyclotron. The results have been analysed with the nuclear optical model and DWBA calculations. The neutron-transfer reactions have been compared with the predictions of the Nilsson model. The results for the pick-up reactions going to the first three levels of 21 Ne are in good agreement with the predictions of the Nilsson model. The RPC model (rotational and particle motion with Coriolis band mixing) modified for pairing effects was employed in an effort to obtain at least a qualitative explanation of the transitions leading to 23 Ne. There are certain large discrepancies consisting of strong transitions that are predicted theoretically under a wide range of assumptions but not seen experimentally. These results indicate that further detailed calculations are necessary to understand the structure of this nucleus.

The (α, n) cross sections on 17O and 18O between 5 and 12.5 MeV

Abstract The excitation functions for the (α, n) reaction on 17 O and 18 O have been measured from 5 to 12 MeV using long counters. Also, the neutron differential cross sections were measured at 9.8, 11.6 and 12.2 MeV, using the Livermore neutron time-of-flight facility. Neutron spectra were obtained every 15° between 3° and 135° with gas targets of enriched 17 O and 18 O. The angular distributions are roughly symmetric about 90°. Small forward peaking is observed at the higher bombarding energies for some of the states, mainly for the ground and first excited states.

Study of the 18O(p,t)16O and 18O(p,d)17O reactions at Ep = 18.2 MeV

Abstract The nuclear reactions 18 O(p,t) 16 O and 18 O(p,d) 17 O have been studied at E p = 18.2 MeV. A gas target of enriched 18 O was used. Triton groups corresponding to the ground state of 16 O, 6.05–6.13 (unresolved), 6.92, 7.12 and 8.88 MeV levels were observed in the (p,t) reaction. The unnatural parity ( J π = 2 − ) state at 8.88 MeV was the weakest (p,t) transition observed. In the (p,d) reaction deuteron groups corresponding to the ground state of 17 O and excited states at 0.871, 3.058 and 3.846 MeV were seen. DWBA analyses of the ground state (p,t) reaction and the first three (p,d) transitions were performed. There was no evidence of a simple pick-up reaction leading to the 3.846 MeV state (J π = 5 2 − ) of 17 O.

Excitation of the ground state band of 19F by 13.9 MeV proton scattering

Abstract The preferential excitation of the ground state rotational band of the 19 F nucleus has been observed in an experiment with 13.9 MeV protons. The angular distributions are fitted with the adiabatic approximation rotational optical model.

Energy levels of 31S and 19Ne

Recently Colli et al., using the 32S(n, d)31P reaction, reported the existence of a 450 keV level in 31P. However, the investigation of other reactions has shown no evidence for such a level. Using the Livermore neutron time-of-flight facility and the (p, n) reaction on 31P, we have searched for the analogue of this proposed level in the mirror nucleus 31S. Neutron spectra were obtained for angles between 30° and 120° and for proton energies from 7.5 to 13.0 MeV. Although the correspondence between the observed levels in 31S and those reported for 31P was excellent up to the maximum excitation energy studied, viz., 3.7 MeV, no evidence for a level at 450 keV excitation was obtained. The reaction 19F(p, n)19Ne also was studied up to an excitation energy of 3.0 MeV in 19Ne. Besides confirming the results obtained by Freeman and West, a previously unreported level at 2.8 MeV was observed.