| Gas-phase isothermal chromatography is a method by which volatile compounds of different chemical elements can be separated according to their volatilities. The technique, coupled with theoretical modeling of the processes occurring in the chromatography column, provides accurate determination of thermodynamic properties (e.g., adsorption enthalpies) for compounds of elements, such as the transactinides, which can only be produced on an atom-at-a-time basis. In addition, the chemical selectivity of the isothermal chromatography technique provides the decontamination from interfering activities necessary for the determination of the nuclear decay properties of isotopes of the transactinide elements.; Volatility measurements were performed on chloride species of Rf and its group 4 homologs, Zr and Hf, as well as Ha and its group 5 homologs, Nb and Ta. Adsorption enthalpies were calculated for all species using a Monte Carlo code simulation based on a microscopic model for gas thermochromatography in open columns with laminar flow of the carrier gas. Preliminary results are presented for Zr- and Nb-bromides.; 30.7-s {dollar}sp{lcub}98{rcub}{dollar}Zr, 7.1-s {dollar}sp{lcub}100{rcub}{dollar}Zr and 15-s {dollar}sp{lcub}99{rcub}{dollar}Nb were produced via the {dollar}sp{lcub}235{rcub}{dollar}U(n,f) Reactions. 38-s {dollar}sp{lcub}162{rcub}{dollar}Hf, 1.7-min {dollar}sp{lcub}165{rcub}{dollar}Hf, 34-s {dollar}sp{lcub}166{rcub}{dollar}Ta, and 1.4-min {dollar}sp{lcub}167{rcub}{dollar}Ta were produced by the {dollar}rmsp{lcub}rm Nat{rcub}Eu+sp{lcub}147{rcub}Sm(sp{lcub}20{rcub}Ne,xn){dollar} Reactions. 65-s {dollar}sp{lcub}261{rcub}{dollar}Rf and 34-s {dollar}sp{lcub}262{rcub}{dollar}Ha were produced via the {dollar}rmsp{lcub}248{rcub}Cm(sp{lcub}18{rcub}O,5n){dollar} and {dollar}rmsp{lcub}249{rcub}Bk(sp{lcub}18{rcub}O,5n){dollar} Reactions, respectively.; The Heavy Element Volatility Instrument (HEVI) was used for these volatility studies. HEVI is an on-line gas chromatography system which continuously separates halide species of short-lived nuclides according to their volatility. The following series in volatility and adsorption enthalpy of the group 4 element chlorides has been established: {dollar}rm ZrClsb4approx RfClsb4>HfClsb4,{dollar} and {dollar}rm ZrClsb4>RfClsb4>HfClsb4,{dollar} respectively. Assuming similar molecular structures for chloride complexes within group 4 of the periodic table, a trend of decreasing volatility and {dollar}rmDelta Hsb{lcub}ads{rcub}{dollar} is observed as one moves down the group (noticed in Zr- and Hf-chlorides). Our results show a break in this expected trend. Further calculations are needed to assess whether this is due to relativistic effects in the transactinide region. |
