On ionic charge distributions of heavy evaporation residues passing through a carbon foil

Charge distributions of Ra recoil ions produced in C12+Pb fusion-evaporation reactions

“…1(a). As we see in the figure, all the predictions [3,4,[7][8][9] are narrower than the experimental ones [10] along with some shifts of the mean charge values. Evidently, a Gaussian cannot describe the asymmetric distributions which are observed with very slow (when Q m → 0) or very fast (when Q m → Z HI ) HIs, as stressed in a number of works (see, for example, [4,5]).…”

“…So the predictive power of the empirical formulas [3,4,[7][8][9] for the equilibrated charges is not quite good for ERs downstream the carbon foil which should equilibrate (normalize) the distributions for ERs emerging from the targets. At the same time, the charge distributions for ERs emerging directly from the targets differ dramatically from the equilibrated ones.…”

“…A number of empirical formulas (mainly for the mean charge Q m and standard deviation σ Q ) was proposed to make up this deficiency (see, for example, Refs. [3][4][5][6][7][8][9]). Note that despite the large number of fitted parameters in the latest formulas [7][8][9]) and their complexity, they reproduce the observed distributions approximately, with an accuracy inadequate sometimes to a practical necessity.…”

“…[3][4][5][6][7][8][9]). Note that despite the large number of fitted parameters in the latest formulas [7][8][9]) and their complexity, they reproduce the observed distributions approximately, with an accuracy inadequate sometimes to a practical necessity. Moreover, in contrast to the first (semiempirical) formulas based on the Thomas-Fermi theory and Bohr's criterion [1,3], the latest ones have no physical grounds, being only based on a fit to the available experimental data.…”

“…Afterwards very broad charge state distributions with high 153 Dy ERs produced in the fusion-evaporation reaction and emerging from the target (histogram) and observed after a carbon reset foil (open circles) as compared to Gaussian approximations according to the parametrization [3,4,[7][8][9] (five different lines of corresponding colors). (b) Charge state distribution of 149 Dy ERs emerging from a La target (full circles) [11].…”