Ion Mobility Measurements and Ion Chemical Reaction Studies at Heavy Elements in a Buffer Gas Cell

Abstract

Drift time measurements of ions in a buffer gas cell filled with argon have been performed from which changes of the ion mobility and ionic radii for various heavy elements and their compounds were determined. The ionic radius of americium shrinks by (3.1 AE 1.3)% with respect to that of plutonium, and an increase of the radius by (28 AE 2)% of plutonium oxide with respect to plutonium was found. Ion chemical reactions of erbium ions were studied online in an argon buffer gas cell to which the reaction gases oxygen (O 2 ) and methane (CH 4 ) were added. The erbium ions were implanted into the buffer gas cell with an energy of 50 MeV. The online measured reaction constant k ErþO2 = (3.2 AE 0.4) Á 10 À10 cm 3 /(molecule Á s) for the reaction Er þ + O 2 ! ErO þ + O agrees with a reference measurement k FT ErþO2 = (3.6 AE 0.4) Á 10 À10 cm 3 / (molecule Á s), performed with a Fourier-Transform-Mass-Spectrometer.

QED and relativistic corrections in superheavy elements

“…There has been two experiments measuring drift time of singly ionized transuranic elements in gases. One mea-sured the relative velocity of Am + with respect to Pu + [75] and an other one measured the same quantity for Cf + and Fm + [18]. The results of these experiments are expressed as…”

“…In some experiments concerning superheavy elements, singly ionized atoms are drifted in a gas cell, under the influence of an electric field. The drift speed can be related, in first approximation, to the charge distribution radius of the ion [75,76]. In this context, it can also be interesting to look at the atomic density, and see how it is affected by relativistic and QED effects.…”

Mobility of the Singly-Charged Lanthanide and Actinide Cations: Trends and Perspectives

“…The latter, however, wrongly predicts a general increase of ionic radii with Z. It is important to mention in this regard the relative measurements of the drift times for the Pu + -Am + and Cf + -Fm + pairs of ions in Ar [26,70]. The HS model estimated the relative contraction of the ionic radii in these pairs as 3.1±1.3 and 2%, respectively.…”

“…For heavy ions, their dependence on Z should reveal the effect of relativistic contraction. Though the effective size of an ion can be extracted from the ab initio interaction potentials themselves, it is important to understand whether or not the transport measurements can provide a systematic means to probe the ionic radii, taking into account exploratory experiments for the actinide ions [26,70] and speculating to the superheavy ions.…”

“…Smoothed data are tabulated by [73] and are also available in the LXCat database [50]. A few relative drift time measurements were carried out [26,70] in Ar for the 255 100 Fm + (5f 12 7s): 251 98 Cf + (5f 10 7s) and 243 95 Am + (5f 7 7s): 239 94 Pu + (5f 6 7s) ion pairs to assess their effective radii. Mobilities of U + ion in all rare gases from He to Xe were also calculated using ab initio interaction potentials [74].…”