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Understanding Molecular Bonding and Excitations for Rotational and Vibrational Dynamics in Molecules

Explore the fascinating world of chemical bonding including ionic and covalent bonds, molecular excitations involving rotation and vibration, and the interplay of electronic, vibration, and rotation in molecules. Discover the properties of ionic and covalent compounds, their characteristics, and differences. Learn about the energy gaps in electronic, vibrational, and rotational excitations. Dive into molecular constants and phenomena like fluorescence and phosphorescence.

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Understanding Molecular Bonding and Excitations for Rotational and Vibrational Dynamics in Molecules

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  1. Molecules E&R Chapter 12

  2. Outline • Bonding 12-1 • Ionic 12-2 • Covalent 12-3 • Molecular Excitations 12-4 • Rotation 12-5 • Vibration 12-6 • Electronic • Electronic + Vibration + Rotation 12-7

  3. Bonding http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/chemcon.html#c1 R Nave, Georgia State Univ

  4. Chemical Bonding http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bondcon.html#c1 R Nave, Georgia State Univ

  5. Ionic Bonds RNave, GSU at http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond.html#c4

  6. Ionic Bonds

  7. Ionic Bonding RNave, Georgia State Univ at hyperphysics.phy-astr.gsu.edu/hbase/molecule

  8. Ionic Bonding a.u. = atomic energy unit = 2*(13.6eV) Brandsen&Joachim

  9. E&R

  10. Covalent Bonds RNave, GSU at http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond.html#c4

  11. Covalent Bonding SYM ASYM spatial spin ASYM SYM spatial spin

  12. Covalent Bonding not really parallel, but spin-symmetric Stot = 1 Stot = 0 not really anti, but spin-asym

  13. Covalent Bonding Bransden&Joachin

  14. Ionic Characteristics Crystalline solids High melting & boiling point Conduct electricity when melted Many soluble in water, but not in non-polar liquids Covalent Characteristics Gases, liquids, non-crystalline solids Low melting & boiling point Poor conductors in all phases Many soluble in non-polar liquids but not water Ionic vs Covalent Bond Properties

  15. Rotational Spectra w rotational A.M. moment of inertia

  16. Rotation

  17. Rotation

  18. Rotational Spectra

  19. Ocean Optics: Nitrogen N2 ~ 0.3 eV ~ 0.4 eV

  20. Vibration

  21. Vibration (in an Electronic state)

  22. Electronic + Vibration

  23. Electronic + Vibration + Rotation 2.550 eV 2.656 eV electronic excitation gap vibrational excitation gaps

  24. Electronic + Vibration + Rotation Vibrational Well Vibrational Well 2.656 eV depth ~ 0.063 eV electronic excitation gap vibrational excitation gaps

  25. Electronic, Vibration, Rotation Electronic ~ optical & UV ~ 1 – 3 eV Vibration ~ IR ~ 10ths of eV Rotation ~ microwave ~ 1000ths of eV

  26. Electronic + Vibration + Rotation 2.550 eV 2.656 eV electronic excitation gap vibrational excitation gaps

  27. ** + Vibration + Rotation IN A DIATOMIC MOLECULE because a photon has one unit of angular momentum, the rotational quantum number must change (vib is not angular motion) Dr = 0 not allowed

  28. ** + Vibration + Rotation

  29. Ocean Optics: Nitrogen N2 ~ 0.3 eV ~ 0.4 eV

  30. Some Molecular Constants Notes: a) vibrational frequency in table is given as f / c b) moment of inertia in table is given as hbar2/(2I) / hc

  31. Fluorescence absorb at one wavelength, emit at another

  32. Phosphorescence tunneling slows the decay process

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