Reactions of 14N and 16O ions with light nuclei at Elab = 16–58 MeV

Yield curves for formation of ⁷Be and other radio-nuclides from bombardment of C, Al and Si targets with 16–58 MeV ¹⁴N and ¹⁶O ions were measured. The ⁷Be yields disagree by several orders of magnitude with Hauser-Feshbach and transition-state predictions. The other yields are in order-of-magnitude agreement with nucleon and/or α-particle evapolation calculations.     

A weight-function approach for determining watershed initial conditions for combustion waves

In many generic combustion models, one finds that a combustionwave will develop with a specific wave speed. However, thereare possible initial temperature profiles which do not evolveinto such waves, but rather die out to the ambient temperature.There can exist, in some models, a clear distinction betweenthose initial conditions that do evolve into combustion wavesand those that do not; this is sometimes referred to as thewatershed initial condition. When fuel consumption is consideredto be negligible, analytical methods can be used to obtain theexact watershed. In this paper, we consider the problem of determiningpseudo-watersheds and ascertaining the relationship betweenthese pseudo-watersheds and the exact watersheds. In the processa novel weight-function approach for infinite spatial domainsis developed.     

First direct observation of strong interaction spin-orbit effects in antiprotonic atoms

The strong ¯p-nucleus spin-orbit interaction was investigated in a measurement of the strong-interaction effects of the 9→8 transition in ¯p ¹⁷⁴Yb at the Low-Energy Antiproton Ring (LEAR) at CERN. This measurement was part of an experimental programme where, for the first time, the fine-structure components of the last observable X-ray transition in a ¯p atom, which carries information on the strong ¯p-nucleus interaction, were resolved and studied individually. The observed splitting ΔE _exp=2408±26 eV consists of the electromagnetic fine-structure splitting ΔE _FS=2350 eV and an additional splitting Δ?=58±26 eV. In addition, one finds a significant difference in the level widths of Δ=195±59 eV with the larger value_?=1216±41 eV for the lower fine-structure level. This experiment follows an earlier measurement on ¯p ¹³⁸Ba, where the transition 8→7 is influenced by the strong interaction. In this case, however, the fine-structure components could not be resolved. The results for¹⁷⁴Yb may be attributed to a spin-orbit (LS) term in the complex strong-interaction potential.     

Activation cross section for 27Al(π+,π0)27Si at 100 MeV

The activation cross section for ${}^{27}\text{Al}\text{(π}{}^{\mathrm{+}}\text{,π}{}^0\text{)}{}^{27}\text{Si at}\text{E}{}_{\mathrm{\pi }}\text{= 99 ± 9}\text{MeV}$ was determined to be 5.1 ± 2.2 mb by counting the residual β⁺ activity of ²⁷Si. This result is compared with other pion-nucleus cross sections. A value for the elementary pion-nucleon cross section inside the nucleus is derived from this result and compared with an estimate from a phenomenological expression.     

Reactions of 14N and 16O ions with p and s-d shell nuclei at Elab = 16 to 75 MeV

Yield curves were measured for formation of ⁷Be and of residual nuclei formed by α-particle and nucleon emission following the reactions of 16 to 75 MeV ¹⁴N and ¹⁶O ions with thick, natural C, Mg, Al and Si targets. The results are discussed in terms of statistical model calculations. Yield curves calculated with computer codes based on the statistical model are compared with the experimental results.