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Electronic Structure of Molecules AST380E Yancy L. Shirley

Electronic Structure of Molecules AST380E Yancy L. Shirley. Where do we find molecules ?. Orion in CO J=2-1. Molecular Clouds & Star Formation Regions. VLT, Japan. Brown Dwarfs: Gliese 229B. CH 4 Absorption. Geballe, et al. 1995. Planetary Atmospheres. Voyager, NASA.

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Electronic Structure of Molecules AST380E Yancy L. Shirley

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  1. Electronic Structure of Molecules AST380E Yancy L. Shirley

  2. Where do we find molecules ? Orion in CO J=2-1 Molecular Clouds & Star Formation Regions VLT, Japan

  3. Brown Dwarfs: Gliese 229B CH4 Absorption Geballe, et al. 1995

  4. Planetary Atmospheres Voyager, NASA ISO Spectrum of Jupiter C2H2 C2H6 CH3D NH3 CH4 PH3

  5. Comets: Hale-Bopp HCN J=4-3 D. Jewitt, U. Hawaii

  6. Evolved Stars: IRC10216 HCN BIMA Image C4H BIMA Image

  7. Why do molecules form? Classical Argument e- + + R Stable molecule has e- with HIGH PROBABILITY of being found between nuclei

  8. The Born-Oppenheimer Approximation e- rA rB p+ + + p+ R The H2+ Hamiltonian ignore Since the mass(p+) >> mass(e-) , we can ignore nuclear motion (the 1st term) and solve Schroedinger’s Eq. assuming a fixed nucleus.

  9. Quantum Calculations of H2 Structure

  10. Molecular Orbitals - LCAO + ANTI-BONDING BONDING + + + +

  11. Anti-bonding p+ repulsion Bonding -13.6 eV Anti-symmetric Energy e- binding Energy Symmetric -54.4 eV Distance (nm) K. Krane, Modern Physics

  12. Electronic State in a molecule L Lz E Electronic orbital angular momenta precess about internuclear axis due to strong electric field. Symbol: s , p , d

  13. s Molecular Orbitals AO MO + + + Z 1s sg1s - + + - Z 1s su1s

  14. s Molecular Orbitals AO MO - + + - - + - 2pz sg2pz - + - + - + - + su2pz 2pz

  15. p Molecular Orbitals AO MO + + + Z - - - pu2px 2px - + - + Z - + - + pg2px

  16. Correlation of Molecular Orbitals - Homonuclear Unified Atom Separated Atom G. Herzberg, Molecular Spectra & Molecular Strucutre , vol I.

  17. Total Electronic Term of a Linear Molecule O L S S L W = |L + S| Total electronic term:

  18. Symmetries of electronic state z -z Inversion yy g y -y y - y u x -x ONLY Applies to homonuclear linear molecules z z Reflection yy + y -y y - y - x x ONLY Applies to linear molecules in S states

  19. H2+ E L = 0 S = ½ 2Sg+ sg1s

  20. H2 E L = 0 S = 0 1Sg+ sg1s

  21. He2+ E su1s L = 0 S = ½ 2Su+ sg1s

  22. C2 E pu2p su2s sg2s su1s L = 0 S = 0 1Sg+ sg1s

  23. N2 E sg2p pu2p su2s sg2s su1s L = 0 S = 0 1Sg+ sg1s

  24. O2 E pg2p L = 0 S = 0 sg2p 1Sg+ pu2p L = 2 S = 0 su2s 1Dg sg2s su1s L = 0 S = 1 3Sg- sg1s Ground State

  25. O2 (pg2p)2Configurations l1 l2 s1 s2 L S 1D 3S 1S

  26. Bond Order Bond Energy Bond Length B2 C2 N2 O2 F2 Ne2 D. McQuarrie, Quantum Chemistry

  27. Correlation of Molecular Orbitals - Heteronuclear Separated Atom Unified Atom G. Herzberg, Molecular Spectra & Molecular Strucutre , vol I.

  28. OH E 2pp 2ps 2ss L = 1 S = ½ 2P 1ss

  29. CO E s2pA p2pA s2sB s2sA s1sB L = 0 S = 0 1Sg+ s1sA

  30. Photoelectron Spectrum CO s2sB s2sA p2pA s2pA # e- ejected Binding Energy D. McQuarrie, Quantum Chemistry

  31. MO Notation D. McQuarrie, Quantum Chemistry

  32. Ground Electronic State of a few Linear Molecules 1S H2, CH+, CO, CS, SiO, HCN, HCO+, N2H+, CO2, HCNH+, HC3N 2S H2+, CN, CO+, CCH 3S O2, NH, SO, CCS, C2O 2P CH, OH, NO

  33. Excited States of H2 E sg2p L = 0 S = 0 C1Pu pu2p L = 0 S = 0 su2s B1Su+ sg2s L = 0 S = 1 su1s b3Su+ sg1s L = 0 S = 0 X1Sg+

  34. UV Electronic Transitions: H2 Lyman Band Werner Band Shu, Radiation

  35. Electronic Transitions: C2 Phillips Band

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