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Study of the electronic structure of the actinide tetrabromides ThBr4 and UBr4 using ultraviolet photoelectron spectroscopy and density functional calculations

Study of the electronic structure of the actinide tetrabromides ThBr4 and UBr4 using ultraviolet photoelectron spectroscopy and density functional calculations
Study of the electronic structure of the actinide tetrabromides ThBr4 and UBr4 using ultraviolet photoelectron spectroscopy and density functional calculations
Ultraviolet photoelectron spectra of UBr4 and ThBr4 have been recorded in the gas-phase and interpreted using relativistic density functional calculations. For ThBr4, eight bands were observed which are interpreted as ionization from the five Br 4p symmetry orbitals of a Br-4 unit in T-d symmetry, with three of the bands [the (4t(2))(-1), (1t(1))(-1), and (3t(2))(-1) ionizations] each being split into two by spin-orbit interaction. The observed splittings are rationalized in terms of the Th 6p and Br 4p contributions to the orbitals and by comparison with the known ultraviolet photoelectron spectra of ThF4 and ThCl4. The first vertical ionization energy (VIE) of ThBr4 was measured as (10.92 +/-0.03) eV. UBr4 shows a very similar photoelectron spectrum with an extra band at (9.65 +/-0.02) eV VIE. This is associated with a (5t(2))(-1) (U 5f,6d) ionization. Supporting matrix isolation infrared experiments were also carried out under very similar vaporization conditions to those used in the photoelectron spectroscopy experiments to check the composition of the vapor beams used. In these experiments, the T-2 stretching modes of ThBr4 and UBr4 have been measured as 230 +/-2 and 239 +/-2 cm(-1), respectively. Both the photoelectron and infrared matrix isolation spectra are consistent with an effective tetrahedral geometry for UBr4 and ThBr4.
perturbation-theory approach, relativistic calculations, tetrahalidesuf4, gaseous thorium, thermochemistry, bromides, thcl4, ucl4, thf4
0021-9606
9832-9839
Beeching, L. J.
1fef872f-d8df-4474-acb2-0a57b17086df
Dyke, J. M.
46393b45-6694-46f3-af20-d7369d26199f
Morris, A.
378f6b9c-92e7-4783-b7be-cafca74b5372
Ogden, J. S.
82db5ee4-1836-4d04-a8ed-281016b93eee
Beeching, L. J.
1fef872f-d8df-4474-acb2-0a57b17086df
Dyke, J. M.
46393b45-6694-46f3-af20-d7369d26199f
Morris, A.
378f6b9c-92e7-4783-b7be-cafca74b5372
Ogden, J. S.
82db5ee4-1836-4d04-a8ed-281016b93eee

Beeching, L. J., Dyke, J. M., Morris, A. and Ogden, J. S. (2001) Study of the electronic structure of the actinide tetrabromides ThBr4 and UBr4 using ultraviolet photoelectron spectroscopy and density functional calculations. The Journal of Chemical Physics, 114 (22), 9832-9839. (doi:10.1063/1.1370945).

Record type: Article

Abstract

Ultraviolet photoelectron spectra of UBr4 and ThBr4 have been recorded in the gas-phase and interpreted using relativistic density functional calculations. For ThBr4, eight bands were observed which are interpreted as ionization from the five Br 4p symmetry orbitals of a Br-4 unit in T-d symmetry, with three of the bands [the (4t(2))(-1), (1t(1))(-1), and (3t(2))(-1) ionizations] each being split into two by spin-orbit interaction. The observed splittings are rationalized in terms of the Th 6p and Br 4p contributions to the orbitals and by comparison with the known ultraviolet photoelectron spectra of ThF4 and ThCl4. The first vertical ionization energy (VIE) of ThBr4 was measured as (10.92 +/-0.03) eV. UBr4 shows a very similar photoelectron spectrum with an extra band at (9.65 +/-0.02) eV VIE. This is associated with a (5t(2))(-1) (U 5f,6d) ionization. Supporting matrix isolation infrared experiments were also carried out under very similar vaporization conditions to those used in the photoelectron spectroscopy experiments to check the composition of the vapor beams used. In these experiments, the T-2 stretching modes of ThBr4 and UBr4 have been measured as 230 +/-2 and 239 +/-2 cm(-1), respectively. Both the photoelectron and infrared matrix isolation spectra are consistent with an effective tetrahedral geometry for UBr4 and ThBr4.

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More information

Published date: 8 June 2001
Keywords: perturbation-theory approach, relativistic calculations, tetrahalidesuf4, gaseous thorium, thermochemistry, bromides, thcl4, ucl4, thf4

Identifiers

Local EPrints ID: 19401
URI: http://eprints.soton.ac.uk/id/eprint/19401
ISSN: 0021-9606
PURE UUID: 983179d2-e8e7-4048-9120-56ab4f14cf44
ORCID for J. M. Dyke: ORCID iD orcid.org/0000-0002-9808-303X

Catalogue record

Date deposited: 14 Feb 2006
Last modified: 16 Mar 2024 02:36

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Contributors

Author: L. J. Beeching
Author: J. M. Dyke ORCID iD
Author: A. Morris
Author: J. S. Ogden

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