Recoil-atom catcher technique

As with Md, the physical separation of the nobelium atoms from the target material can be made using the recoil-atom catcher technique. It is preferable to combine this with the gas jet technique since the atoms are deposited on the catcher foil in nearly a monolayer and can be easily rinsed off the surface with dilute acid without complete dissolution of the foil. Isolation of the No from other actinides produced in the bombardment and from any target material transferred to the foil can be readily made using schemes based on the separation of divalent ions from trivalent ones, e.g. selective elution by solvent extraction chromatography using HDEHP as the stationary organic phase and 0.05 n HCl... 

The amount of Es available at this time was very small about N = 10 atoms (a 4- 10 g). At a flux density of a particles = 10 " cm s , a cross section (Ta n = 1 mb and an irradiation time of 10 s a yield N

single atoms, the recoil technique was applied (Fig. 14.6). Es was electrolytically deposited on a thin gold foil. The recoiling atoms of Md were sampled on a catcher foil. After irradiation, the catcher foil was dissolved and Md was separated on a cation-exchange resin. In 8 experiments 17 atoms of Md were detected and identified by their transmutation into the spontaneously fissioning the properties of which were known ... 

In these experiments, the recoil technique was modified into a double recoil technique by application of a moving belt (Fig. 14.7). The recoiling atoms generated by the heavy-ion reaction (first recoil) are deposited on the belt and transported along a catcher foil on which the recoiling atoms from a decay (second recoil) are collected. From the activity recorded as a function of the distance, the half-life can be calculated. 

A new technique was used that allowed the atoms of Md to recoil from the very thin target onto a "catcher" foil. Thirteen atoms of Md (ti 1.3 h) were made in 9 h of irradiation and isolated by rapid elution from a colunm of cation exchange resin using a solution of of-hydroxy isobutyric acid. The elution showed 5 atoms of element 101 (identified by the spontaneous fission of the daughter f m) and 8 atoms of the Fm daughter (Fig. 16.7 eqn. (16.10)). The recoil — ion exchange technique used in... 

Instead of implanting a recoiling heavy nucleus into a silicon detector it can be stopped in a gas volume. Transport from this gas-catcher to a gas chromatographic system then requires either a suitably volatile compound to be formed or transport via aerosols. Elements in groups 12-18 may even be transported directly in atomic form [71]. This introduces a chemical selectivity into the system which can be employed to greatly enhance the selectivity of the experiment. One big advantage of such a system is its continuous operation. Experimental details of such techniques are discussed in Experimental Techniques and results are outlined in Gas-Phase Chemistry of Superheavy Elements . 

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