1. Thermodynamic data evaluation for chemical RIB purification
- the experimentalists approach
R. Eichler1,2,*, J. Neuhausen1
1Laboratory for Radio- and Environmental Chemistry, Paul Scherrer Institute Villigen, CH-5232, Switzerland
2Department for Chemistry and Biochemistry, University Bern, CH-3012, Switzerland

2. Outline
1. Introduction
Adsorption interactions:
A) Covalent coordinative bond
B) Dispersion interaction
C) Metal bond
3. Summary

3. Boundary conditions - needs
Transactinide chemistry?
Chemical RIB Purification
* Simple volatile species (element or compound)
* Formation and release properties –
Thermodynamics and Kinetics
* Source design – materials –
Reaction and Adsorption
* Chemical separation –
Volatility and Adsorption

4. Gas phase Chemistry of transactinides1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 H Li Na K Rb Cs Fr Be Mg Ca Sr Ba Ra Sc Y
La*
Ac** Ti Zr Hf V Nb Ta Cr Mo W Mn Tc Re Fe Ru Os Co Rh Ir Ni Pd Pt Cu Ag Au Zn Cd Hg He Ne Ar Kr Xe Rn B Al Ga In Tl C Si Ge Sn Pb N P As Sb Bi O S Se Po F Cl Br I At Te Ce Th Pr Pa Nd U Pm Np Sm Eu Am Gd Cm Tb Bk Dy Cf Ho Es Er Fm Tm Md Yb No Lu Lr Pu * ** Rf Db Sg Mt Ds Rg Bh Hs
112
114
116
113
115
elements
compounds

5. Isothermal gas chromatography
yield
External chromatogram
T=300K
Detector
50%
T=600K
T50
Result: T50  DHads

6. Thermochromatography
yield
length
T=300K
Temperature gradient
T=100K
Internal chromatogram
Tdep
detectors
Result: Tdep  DHads
Volatility wanted!

7. Kinetic model of gas adsorption chromatography
Monte Carlo Simulation
Condition :
* Simple reversible single step adsorption process
i.e. No change of the chemical state during the process and no
irreversible reaction with the surface or diffusion into the surface
* zero surface coverage / carrier free amounts = single atoms
no phonon frequency
Frenkel-type adsorption kinetics:
a= 1/no*exp(-DHads/RT)
phonon frequency of the surface
material : no
-> sticking probability if needed
for short-lived isotopes
radioactive decay: t1/2
else: texp
gas transport through tubes:
laminar flow
DHads
diffusion in the carrier gas
Gilliland eqn.
Zvara, I., Radiochim. Acta 38, 95 (1985).

8. Gas phase Chemistry of Transactinides1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Tc Re Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba
La* Hf Ta W Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra
Ac** Rf Db Sg Bh Hs Mt Ds Rg
112
113
114
115
116
118 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu * ** Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Element Compound Surface Method
Rf RfOX2, RfX4 quartz TC,IC
Db DbOX3, DbX5 quartz TC,IC
Sg SgO2X2 quartz TC,IC
Bh BhOCl3 quartz IC
Hs HsO4 quartz TC
Hg/Pb/Bi/Po/At/Rn gold/quartz TC, IC

9. Adsorption interactions
Chemisorption
-DHads > 30 kJ/mol
Physisorption
DHads< 30 kJ/mol EA
EDB
Eads re re r
A) Covalent coordinative bond
C) Metal bond
B) Dispersion interaction

10. Gas phase Chemistry of Transactinides1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Tc Re Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba
La* Hf Ta W Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra
Ac** Rf Db Sg Bh Hs Mt Ds Rg
112
113
114
115
116
118 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu * ** Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Element Compound Surface Method
Rf RfOX2, RfX4 quartz TC,IC
Db DbOX3, DbX5 quartz TC,IC
Sg SgO2X2 quartz TC,IC
Bh BhOCl3 quartz IC
Hs HsO4 quartz TC
Hg/Pb/Bi/Po/At/Rn gold/quartz TC,IC
Bond Character
Chemisorption
Physisorption
Chemisorption/

11. A) Covalent coordinative bond
transition element compounds
in highest oxidation states
-DH0(s) s
-DH0(g)
DHsubl g
5th period
6th period
7th period
-DH0(g), monoatomic metal gases

12. A) Covalent coordinative bondDb Rf Ta Hf Zr Nb Sg W Mo Bh Re Hs Tc Os Ru

13. A) Covalent coordinative bond
quartz surface
RfCl4
BhO3Cl
SgO2Cl2
DbOCl3
Eichler, B. et al.: J. Phys. Chem. A 103(46), 9296 (1999).

14. A) Covalent coordinative bond
quartz surface
HsO4
Eichler, R. et al.: Radiochim. Acta 87, 151 (1999).

15. B) Dispersion interaction
Inert atoms on
metal surfaces:
Atoms/molecules on
dielectric surfaces:
EA/B … effective excitation energy  EA/B = IPA/B*;
g = 1 for metals;
a … polarizability of the adsorbate;
IPA/B … ionisation potentials;
re … distance between the adsorbate to the substrate;
e … dielectric constant of surface material
*Pauling, L. Science 1961, 134 (3471), 15.

16. B) Dispersion interaction
re = 240pm (van der Waals radius of Rn)

17. B) Dispersion interaction
Adhesion model
Description of DHads proportional to the enthalpy of adhesion:
Dgad(A,B) = -2 F (g0(A) g0(B))1/2
... dissimilarity parameter (calculated)
g0... surface energy at T=0 K
F ... geometrical factor (empirically 0.31)
VA ... Volume of the spherical adsorbate atom
DHads = 0.71*109 F F VA2/3 (g0(A) g0(B))1/2
 DHMads(Z) / DHMads(Xe) = C(Z,Xe)
Z Ne Ar Kr Xe
C(Z,Xe)
A.R. Miedema, B.E. Nieuwenhuys Surf. Sci. 104, (1981).

18. B) Dispersion interaction Adhesion model extendedZ Ne Ar Kr Xe Rn
C(Z,Xe)
0.17
0.52
0.72 1
1.11
Haettig, C. J. Phys. Chem. A 1996, 100 (15), 6243.
Nicklass, A.J. Chem. Phys. 1995, 102 (22), 8942.

19. B) Dispersion interactionZ Ne Ar Kr Xe Rn
C(Z,Xe)
0.17
0.52
0.72 1
1.11

20. B) Dispersion interactionZ Ne Ar Kr Xe
112
114
C(Z,Xe)
0.17
0.52
0.72 1
1.04
1.2
Seth, M.,Schwerdtfeger, P.: J. Chem. Phys. 1997, 106 (9), 3623.
Eliav, E. et al. Phys. Rev. A 1995, 52 (4), R. Eichler, J. Phys. Chem B. 106, 5413 (2004).

21. C) Metal bond Metallic character (DHo298(g)-0.5*DHodiss)/DHo298(g)
dimer formation (non metals)  lattice formation (metals)
Eichler, B.: Kernenergie 19, 307 (1976).

22. C) Metal bond
Enthalpy diagram of Release and Adsorption Processes (Elements on Metals)
Experiment
Hads=HN+HD
HV=-Hsolv-HD IN ON

23. Eichler/Miedema model: Adsorption
C) Metal bond:
Eichler/Miedema model: Adsorption B A
DHnettoads
solid state  adsorbed state
criterion DHsol> 50 kJ/mol B A
criterion DHsol< 50 kJ/mol
Eichler, B., Rossbach, H.: Radiochim. Acta 33, 121 (1983)

24. Miedema model: Intermetallic solid solution
C) Metal bond
Miedema model: Intermetallic solid solution
at infinite dilution B B B B A A B B B B
Semi empirical model adjusted
to hundreds of binary systems
VA atomic volume
VAsol… atomic volume in solution
nWS … electron density at Wigner Seitz cell boundaries
F… electronegativities (Miedema scale)
Rm… hybridization term (empirical, combination dependent)
A.R. Miedema, J. Less-Comm. Met. 46, 67 (1975)

25. Eichler B.: PSI Report 03-01; Villigen (2002), ISSN 1019-0643.
C) Metal bond
nWS … electron density at Wigner Seitz cell boundaries
Theoretical:
Self consistent electronic structure calculations
Experimental:
nws [d.u.] = 10-2(B/V)1/2
B = bulk modulus
V = molar volume [cm3/mole]
Empirical:
nWS = * A1/2 * (r12/V) * exp (7.03 – (So(s)/ (3*R)))
r12 = c + a ln(A) + b So(s)
V = (4/3 ) p r12 3 / R*
Eichler, B., Rossbach, H.: Radiochim. Acta 33, 121 (1983)
Eichler B.: PSI Report 03-01; Villigen (2002), ISSN

26. Derivation of Miedema Electronegativity Parameters
C) Metal bond
Derivation of Miedema Electronegativity Parameters
From various electronegativity scales:
Allred-Rochow
Pauling
Allen
Pearson
Sanderson

27. C) Metal bond
Noble gases, halogens excluded “0”

28. C) Metal bond
Noble gases, halogens excluded “0”

29. Korrelation –DHads(Au) with DHsubl
C) Metal bond
Korrelation –DHads(Au) with DHsubl
DHnettoads<50kJ/mol

30. B+C) Metal bond + Dispersion interaction
R. Eichler Radiochim. Acta 93, 245–248 (2005)

31. Release Enthalpy
DHf =DHSubl - DHSol

32. Release Enthalpy

33. Off-line Release studies

34. C) Metal bond Experiment/Eichler-Miedema Empirically or tables
Born-Haber cycle
Eichler-Miedema

35. A/B) coordinative / physisorption
Elements on quartz
Soverna, S., PhD-thesis, University Bern, Bern (2004).

36. Hot Targets Intermetallic compounds with Rh
[1] B. Eichler, PSI Report 03-01, Villigen, 2003