title: Ab initio calculations on SF2 and its low-lying cationic states: anharmonic Franck-Condon simulation of the UV photoelectron spectrum of SF2.
abstract: Geometry optimization calculations were carried out on the (approximate)X(1)A(1) state of SF2 and the (approximate)X(2)B(1), (approximate)A(2)A(1), (approximate)B(2)B(2), (approximate)C(2)B(2), (approximate)D(2)A(1), and (approximate)E(2)A(2) states of SF2(+) employing the restricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] method and basis sets of up to the augmented correlation-consistent polarized quintuple-zeta [aug-cc-pV(5+d)Z] quality. Effects of core electron (S 2s(2)2p(6) and F 1s(2) electrons) correlation and basis set extension to the complete basis set limit on the computed minimum-energy geometries and relative electronic energies (adiabatic and vertical ionization energies) were investigated. RCCSD(T) potential energy functions (PEFs) were calculated for the (approximate)X(1)A(1) state of SF2 and the low-lying states of SF2(+) listed above employing the aug-cc-pV(5+d)Z and aug-cc-pV5Z basis sets for S and F, respectively. Anharmonic vibrational wave functions of these neutral and cationic states of SF2, and Franck-Condon (FC) factors of the lowest four one-electron allowed neutral photoionizations were computed employing the RCCSD(T) PEFs. Calculated FC factors with allowance for Duschinsky rotation and anharmonicity were used to simulate the first four photoelectron bands of SF2. The agreement between the simulated and observed first bands in the He I photoelectron spectrum reported by de Leeuw et al. [Chem. Phys. 34, 287 (1978)] is excellent. Our calculations largely support assignments made by de Leeuw et al. on the higher ionization energy bands of SF2.
authors.affiliation: Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hung Hom, Hong Kong. epl@soton.ac.uk
authors.forename: Edmond P F
authors.initials: EP
authors.lastname: Lee
authors.forename: Daniel K W
authors.initials: DK
authors.lastname: Mok
authors.forename: Foo-tim
authors.initials: FT
authors.lastname: Chau
authors.forename: John M
authors.initials: JM
authors.lastname: Dyke
mesh_terms: D002412:Cations / Q000737:chemistry; D003198:Computer Simulation; D004583:Electrons; D005459:Fluorides / Q000737:chemistry*; D010777:Photochemistry; D013057:Spectrum Analysis; D013457:Sulfur Compounds / Q000737:chemistry*; D014466:Ultraviolet Rays; D014732:Vibration
chemical_list: D002412:Cations; D013457:Sulfur Compounds; C523090:sulfur fluoride; D005459:Fluorides