Abstract:In this paper we present relativistic core ab initio model potentials based on atomic Cowan-Griffin calculations, together with Wood-Boring spin-orbit operators and optimized Gaussian valence basis sets, for the lanthanide elements Ce to Lu and for the actinide elements Th to Lr. This completes the chemically relevant part of the Periodic Table. A ͓Kr,4d͔ core was chosen for Ce-Lu and a ͓Xe,4f ,5d͔ core was chosen for Th-Lr. Minimal (14s10p9d8 f )/͓2s1 p1d1 f ͔ and (14s10p11d9 f )/͓2s1 p1d1 f ͔ valence basis s… Show more
“…These large rates imply an additional spin relaxation mechanism other than spin exchange, dipolar relaxation, and second-order spin-orbit coupling, which are well known from studies with alkali metal atoms. The electrostatic quadrupole-quadrupole interaction is a long-range mechanism for driving inelastic processes in L = 0 atoms, such as seen in metastable alkaline earth metal systems [11], however, the anisotropic charge distribution in submerged-shell atoms is confined tightly near the nucleus [12]. Thus while the quadrupole-quadrupole interaction is not expected to be shielded, the interaction strength should be far weaker than in outer-shell systems.…”
The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters. Spin relaxation due to atom-atom collisions is measured for magnetically trapped erbium and thulium atoms at a temperature near 500 mK. The rate constants for Er-Er and Tm-Tm collisions are 3.0 × 10 −10 and 1.1 × 10 −10 cm 3 s −1 , respectively, 2-3 orders of magnitude larger than those observed for highly magnetic S-state atoms. This is strong evidence for an additional, dominant, spin relaxation mechanism, electronic interaction anisotropy, in collisions between these "submerged-shell," L = 0 atoms. These large spin relaxation rates imply that evaporative cooling of these atoms in a magnetic trap will be highly inefficient.
“…These large rates imply an additional spin relaxation mechanism other than spin exchange, dipolar relaxation, and second-order spin-orbit coupling, which are well known from studies with alkali metal atoms. The electrostatic quadrupole-quadrupole interaction is a long-range mechanism for driving inelastic processes in L = 0 atoms, such as seen in metastable alkaline earth metal systems [11], however, the anisotropic charge distribution in submerged-shell atoms is confined tightly near the nucleus [12]. Thus while the quadrupole-quadrupole interaction is not expected to be shielded, the interaction strength should be far weaker than in outer-shell systems.…”
The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters. Spin relaxation due to atom-atom collisions is measured for magnetically trapped erbium and thulium atoms at a temperature near 500 mK. The rate constants for Er-Er and Tm-Tm collisions are 3.0 × 10 −10 and 1.1 × 10 −10 cm 3 s −1 , respectively, 2-3 orders of magnitude larger than those observed for highly magnetic S-state atoms. This is strong evidence for an additional, dominant, spin relaxation mechanism, electronic interaction anisotropy, in collisions between these "submerged-shell," L = 0 atoms. These large spin relaxation rates imply that evaporative cooling of these atoms in a magnetic trap will be highly inefficient.
“…27 For Pa, we observed that whereas the 5 f orbitals of neutral Pa 5 f 3 6d 1 7s 1 Ϫ 6 L obtained in Ref. 18 sis set with respect to that in Ref. 18.…”
Section: A Embedding Potentialmentioning
confidence: 57%
“…26 B. The "PaCl 6 … 2À defect cluster Relativistic Cowan-Griffin-Wood-Boring 16,17 -based core AIMPs were used for both Pa ͓͑Xe, 4 f , 5d͔ core͒ 18 and Cl ͓͑Ne͔ core͒. 27 For Pa, we observed that whereas the 5 f orbitals of neutral Pa 5 f 3 6d 1 7s 1 Ϫ 6 L obtained in Ref.…”
Section: A Embedding Potentialmentioning
confidence: 81%
“…18 sis set with respect to that in Ref. 18. 28 With the new d basis set and 6d spin-orbit operator, the atomic 6d spin-orbit coupling constant, 6d ϭ͗6d͉V 6d SO ͉6d͘, is 3042 cm Ϫ1 , identical to the Cowan-Griffin-Wood-Boring numerical one, and significantly larger than that of neutral Pa(5 f 3 6d 1 7s 1 Ϫ 6 L), 1199 cm Ϫ1 .…”
Section: A Embedding Potentialmentioning
confidence: 98%
“…Recently, the relativistic core ab initio model potentials of the lanthanide and actinide elements based on Cowan-Griffin-Wood-Boring 16,17 atomic calculations have been published and their good performance in scalar relativistic effects has been pointed out. 18 Whereas the quality of the spin-orbit operators is good for the lanthanides, 19 it has not yet been tested for the actinide elements.…”
In this paper we present the results of spin-orbit relativistic ab initio model potential embedded cluster calculations on (PaCl 6 ) 2Ϫ embedded in a reliable representation of the Cs 2 ZrCl 6 host. Totally symmetric local distortions and vibrational frequencies are calculated for all the states of the 5 f 1 and 6d 1 manifolds, as well as the corresponding 5 f ↔6d transition energies and the shape of the 5 f (⌫ 8u )←6d(⌫ 8g ) fluorescence band. An excellent overall agreement with available experimental data is observed which allows us to conclude that the quality of the spin-orbit operators used is very high for actinide elements, as was already known for transition metal and lanthanide elements. Furthermore, it is concluded that the structural and spectroscopic information produced here is very reliable and that the 6d(⌫ 8g Ј ) state is around 10 000 cm Ϫ1 higher in energy than it was thought; our calculations suggest a value of 30 000 cm Ϫ1 for the 10Dq parameter of Pa 4ϩ in Cs 2 ZrCl 6 , which would be compatible with the lower limit of 20 000 cm Ϫ1 accepted for Ce 3ϩ in Cs 2 NaYCl 6 .
First‐principles and semiempirical relativistic quantum chemical methods applicable to molecular systems containing lanthanides and actinides are briefly reviewed. Selected recent applications of some of these methods are discussed.
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