Theoretical Studies of Electronic Spectra and Bonding in AlCl/AlF Jeff Leiding, D. E. Woon and T. H. Dunning, Jr. University of Illinois at Urbana-Champaign

Introduction 1.AlCl and AlF discovered in circumstellar envelope of the carbon star IRC ,2 2.AlF observed in sunspot umbra 3 3.AlCl and AlF exhibit interesting bonding which we can explain with recoupled pair bonding (RPB) 4.Experimentally well-studied systems: Good for benchmarking of theory 1.Cernicharo et al., Astron. Astrophys. 1987, 183, L10. 2.Ziurys et al., Astrophys. J. 1994, 433, Bagare et al., Solar Phys. 2006, 234, 1.

Introduction Why are the excited states bound, and by so much?

Outline 1.Methodology 2.Recoupled pair bonding of AlCl/AlF 3.Quantitative agreement of theoretical AlCl/AlF spectroscopic parameters with experiment 4.Theoretical term values of AlF compared to experiment

Methods CASSCF/MRCI+Q aug-cc-pwCV5Z Transform CAS orbitals into GVB orbitals: singly occupied, atom-centered Rovibrational levels calculated with “LEVEL” program 1 on ab initio PECs 1.R. J. Le Roy, LEVEL, Numerical Eigenvalue and Eigenvector Programme for linear Molecules (University of Waterloo, Ontario, 1986).

AlF Bonding GVB diagrams

AlF Bonding GVB diagrams (3s 2 - λ2 p z 2 )

AlF Bonding GVB diagrams (3s 2 - λ2 p z 2 )

AlF Bonding GVB diagrams 3 Π  GVB orbitals Al 3s 2 pair (3s 2 - λ2 p z 2 )

AlF Recoupled GVB Orbitals 3 Π  Orbitals S=0.733 S=0.789 S=0.859 GVB L GVB R MO/GVB Occupation=1 Al 3s 2 pair coupled rere

AlF Recoupled GVB Orbitals S=0.733 S=0.789 S=0.859 GVB L GVB R MO/GVB Occupation=1 Al 3s 2 pair coupled rere 3 Π  Orbitals

AlF Recoupled GVB Orbitals S=0.733 S=0.789 S=0.859 GVB L GVB R MO/GVB Occupation=1 Al 3s 2 pair coupled rere 3 Π  Orbitals

AlCl Bonding 3 Π GVB orbitals Al 3s 2 pair GVB diagrams

AlCl Recoupled GVB Orbitals S=0.731 S=0.793 S=0.859 GVB L GVB R Occupation=1 Al 3s 2 pair coupled 3 Π  Orbitals MO/GVB rere

Theory/Experimental Agreement 1.Wyse, F. C. et al. J. Chem. Phys. 1970, 52, Murad, E. et al. J. Chem. Phys. 1966, 45, Huber, K. P., Herzberg, G. "Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules,” X1Σ+X1Σ+ a3Πa3Π A1ΠA1Π TheoryExpTheoryExp 3 TheoryExp 3 re(Å)re(Å) T e (cm -1 ) ω e (cm -1 ) ω e x e (cm -1 ) B e (cm -1 ) α e (cm -1 ) D 0 (kcal/mol) ± AlF

Theory/Experimental Agreement 1.Wyse, F. C. et al. J. Chem. Phys. 1970, 52, Murad, E. et al. J. Chem. Phys. 1966, 45, Huber, K. P., Herzberg, G. "Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules,” X1Σ+X1Σ+ a3Πa3Π A1ΠA1Π TheoryExpTheoryExp 3 TheoryExp 3 re(Å)re(Å) T e (cm -1 ) ω e (cm -1 ) ω e x e (cm -1 ) B e (cm -1 ) α e (cm -1 ) D 0 (kcal/mol) ± AlF

Theory/Experimental Agreement 1.Wyse, F. C. et al. J. Chem. Phys. 1970, 52, Murad, E. et al. J. Chem. Phys. 1966, 45, Huber, K. P., Herzberg, G. "Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules,” X1Σ+X1Σ+ a3Πa3Π A1ΠA1Π TheoryExpTheoryExp 3 TheoryExp 3 re(Å)re(Å) T e (cm -1 ) ω e (cm -1 ) ω e x e (cm -1 ) B e (cm -1 ) α e (cm -1 ) D 0 (kcal/mol) ± AlF

Theory/Experimental Agreement 1.Wyse, F. C. et al. J. Chem. Phys. 1970, 52, Murad, E. et al. J. Chem. Phys. 1966, 45, Huber, K. P., Herzberg, G. "Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules,” X1Σ+X1Σ+ a3Πa3Π A1ΠA1Π TheoryExpTheoryExp 3 TheoryExp 3 re(Å)re(Å) T e (cm -1 ) ω e (cm -1 ) ω e x e (cm -1 ) B e (cm -1 ) α e (cm -1 ) D 0 (kcal/mol) ± AlF

Theory/Experimental Agreement 1.Wyse, F. C. et al. J. Chem. Phys. 1970, 52, Murad, E. et al. J. Chem. Phys. 1966, 45, Huber, K. P., Herzberg, G. "Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules,” X1Σ+X1Σ+ a3Πa3Π A1ΠA1Π TheoryExpTheoryExp 3 TheoryExp 3 re(Å)re(Å) T e (cm -1 ) ω e (cm -1 ) ω e x e (cm -1 ) B e (cm -1 ) α e (cm -1 ) D 0 (kcal/mol) ± AlF

AlF (A 1 Π  v  Term Values JExpTheo+Te(exp) Calculated rovibrational levels for J=1-70 Ab initio RMSE~2.0 cm -1 Barrow et al. Physica Scripta. 1974, 10, 86. Pure rotational spectrum of X 1 Σ + error ~10 -3 cm -1

AlF (A 1 Π  v  Term Values JExpTheo+Te(exp) JExpTheo corrected RMSE~0.02 cm -1 Calculated rovibrational levels for J=1-70 Ab initioCorrected ab initio RMSE~2.0 cm -1 Barrow et al. Physica Scripta. 1974, 10, 86. Pure rotational spectrum of X 1 Σ + error ~10 -3 cm -1

Conclusions AlF/AlCl excited states bound by recoupled pair bonding Understand the existence and behavior of excited states based on this insight Theoretical results show excellent agreement with experiment

Acknowledgements Professor Thom DunningProfessor Thom Dunning Dr. David WoonDr. David Woon Dr. Lina ChenDr. Lina Chen Dunning GroupDunning Group Funding: NCSA, Distinguished Chair for Research Excellence in ChemistryFunding: NCSA, Distinguished Chair for Research Excellence in Chemistry

Other Dunning Group Talks RI04(Lu Xu): s 2 recouplingRI04(Lu Xu): s 2 recoupling RI12(David Woon): HZnCH 3RI12(David Woon): HZnCH 3 RI11(Beth Lindquist): Correlation of recoupling ability and ligand propertiesRI11(Beth Lindquist): Correlation of recoupling ability and ligand properties FB02(Tyler Takeshita): SF n OFB02(Tyler Takeshita): SF n O C Zn s 2 recoupling