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

Abstract

Charge state distributions of the Ra recoil ions produced in the 12 C + Pb fusion-evaporation reactions have been obtained by measuring their yields as a function of the high voltage applied to an electrostatic deflector. Well-defined two-humped yield curves for evaporation residues (ERs) were observed. Such observations can be explained by the different sets of charge states inherent in Ra recoil ions. These charge sets correspond to the equilibrated and nonequilibrated components, as earlier observed for evaporation residues produced in different reactions. The main parameters of the distributions (mean charge values, widths, and relative intensities) for both components have been estimated using Monte Carlo simulations of the transmission of the Ra recoil ions through the deflector. For the equilibrated component the values of the mean charge and width are close to those given by different empirical systematics. For the nonequilibrated component these parameters have been obtained for the first time. The additional nonequilibrated ionization is presumably due to the formation of inner shell vacancies produced by the internal conversion of nuclear isomeric transitions of ERs. Nonequilibrated charge parameters obtained for Ra recoil ions are compared to similar available experimental data and some theoretical predictions.

Empirical relationships for heavy-ion equilibrated charges and charge-changing cross-sections in rarefied hydrogen and their application

“…It is assumed that ERs knocked out from a target by heavy ion (HI) projectiles have a very broad charge state distribution. Besides the equilibrated 'solid' component [13][14][15], ERs have much higher charge states corresponding to the non-equilibrated component [16][17][18][19][20]. This component arises from the inner atomic shells ionization induced by the conversion of nuclear transitions in ERs.…”

“…In further consideration, it was assumed that the reliable initial charge state distribution for ionized 252 No ERs escaping the 208 Pb target is the composition of the 'normal solid' component and of the non-equilibrated one. The 'normal solid' component corresponds to the equilibrated charge-state distribution for HIs passed through a solid [13][14][15], whereas the non-equilibrated component has charges which are much higher than 'normal' ones [16][17][18][19][20] (see Section I). The analysis of charge state distributions for ERs of different masses and velocities showed that the number of charge states for the non-equilibrated component N neq exceeds those for the equilibrated one N eq by a factor of 2-4.…”

“…The analysis of charge state distributions for ERs of different masses and velocities showed that the number of charge states for the non-equilibrated component N neq exceeds those for the equilibrated one N eq by a factor of 2-4. Mean charges q neq m and standard deviations σ neq q of the non-equilibrated component also exceed the same parameters of the equi- librated one q eq m and σ eq q within the same factor [19,20]. In subsequent simulations for 252 No ERs escaping the 208 Pb target, it was assumed that N neq = 2N eq .…”

“…In general, ERs escaping a target have a very broad charge state distribution. In addition to the equilibrated 'solid' component (see, for example, [13][14][15]), there is a non-equilibrated one with charge states much higher than those inherent in the equilibrated charges [16][17][18][19][20]. This non-equilibrated component corresponds to excited nuclear states, which strongly affect the ionization of inner atomic shells owing to the conversion of nuclear transitions in ERs.…”

Disentangling the bulk and exit surface contribution on projectile-charge-state evolution

“…These reviews provide a crucial theoretical background in terms of the data collection to date. The CSDs are normally measured by the standard electromagnetic techniques [21][22][23][24] and in order to understand the measured equilibrium charge state data, many empirical formulas such as Thomas-Fermi model, Bohr model, Betz model, Nikolaev-Dmitriev model, To-Drouin model, Shima-Ishihara-Mikumo model, Itoh model, Ziegler-Biersack-Littmark model, Schiwietz model, etc., have been developed in tune with the experimental results from electromagnetic measurements [25 and references therein]. Interestingly, in some distinct cases, like, calculation of non-equilibrium charge state distribution [26,27], estimation of equilibrium target thickness [28], etc., the empirical predictions readily fail to estimate desired parameters.…”