Excitation Functions, Recoil Ranges, and Statistical Theory Analysis of Reactions Induced inFe56with 6-29-MeVHe3Ions

Abstract

Excitation functions and integral recoil ranges have been measured for products of the (${\mathrm{He}}^3$, $p$), (${\mathrm{He}}^3$, $\mathrm{pn}$), (${\mathrm{He}}^3$, $p2n$), (${\mathrm{He}}^3$, $2n$), and (${\mathrm{He}}^3$, $3n$) reactions of ${\mathrm{Fe}}^{56}$. The ${\mathrm{He}}^3$ kinetic energies varied between 6 and 29 MeV. Targets were 99.7% enriched ${\mathrm{Fe}}^{56}$, electroplated on 0.2-mil gold foils. The experimental recoil ranges of reaction products formed between the corresponding reaction thresholds and excitation function peaks are compared with the ranges predicted by the theory of Lindhard, Scharff, and Schiøtt; the ranges are in agreement with the theoretical predictions within the ±10% uncertainty of the experimental measurements. With the exception of the ${\mathrm{Co}}^{57}$ ranges resulting from ${\mathrm{He}}^3$ ion bombardment at energies greater than 25 MeV, all ranges are consistent with a predominantly full-momentum-transfer mechanism with 90° symmetry for emitted particles. The sensitivity of the experimental ranges to reaction mechanism is discussed, as is the influence on range of nucleon evaporation. The excitation functions for the production of ${\mathrm{Ni}}^{56}$, ${\mathrm{Co}}^{56}$, ${\mathrm{Ni}}^{57}$, ${\mathrm{Co}}^{57}$, and ${\mathrm{Co}}^{58}$ have been compared with three sets of statistical-theory calculations. The first set of calculations was a conventional Weisskopf evaporation calculation in which a level density of the form $\rho (E, J)\propto \mathrm{}(2J+1)\mathrm{}{E}^{-2\mathrm{}}\exp \left[2\mathrm{}{\mathrm{}\left(\mathrm{aE}\right)\mathrm{}}^{\frac{1}{2}}\right]$ was used. The calculated excitation functions attained their maximum yields at lower energies than the corresponding experimental excitation functions, as had been noted for similar calculations for ${\mathrm{He}}^4$-induced reactions of ${\mathrm{Fe}}^{56}$ and ${\mathrm{Ni}}^{58}$. A correlation is shown to exist between the displacement of calculated and experimental excitation functions and average rotational energy for the three systems. In the second set of calculations a level density of the form

Keywords

• EXCITATION FUNCTIONS
• RECOIL RANGES
• THEORY ANALYSIS
• HE3 IONS
• MEV HE3
• STATISTICAL THEORY
• REACTIONS INDUCED

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