C566lecture26mt2review

C566lecture26mt2review - Review for Midterm 2 Topics...

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1 Review for Midterm 2 Topics covered since Midterm 1: 1. Rotational structure in vibrational transitions in polyatomics 2. Electronic structure of diatomic molecules (homonuclear and heteronuclear) 3. Electronic spectroscopy selection rules for diatomics 4. Vibrational coarse structure and ro-vibrational fine structure in electronic transitions of diatomics 5. Lambda splitting and spin-orbit splitting in diatomics 6. Electronic structure of polyatomics (requires memory of molecular symmetry concepts) 7. Electronic spectroscopy selection rules for polyatomics 8. Vibrational structure in electronic transitions 9. Forbidden transitions (Herzberg-Teller intensity borrowing) 10. Ro-vibrational fine structure in electronic transitions Other base concepts you need to keep in mind Speed of light = 3 x 10 8 m s 1 =  Visible light is on the order of 500 nm = 5 x 10 -7 m Molecular sizes are on the order of 10 10 m (1 Å) 1 cm 1 = 1.986 x 10 -23 J = 0.01196 kJ mol -1 = 1.12398 x 10 -4 eV k = 1.38 x 10 -23 J K -1 = 0.69 cm -1 K -1 re-Marination of the material to date Several areas in which electronic spectroscopy is important/relevant Photochemistry relevant to Global climate modeling, ozone hole formation and remediation (secondary aerosol formation, radical formation) Chemical dynamics
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2 Structural determination of just about everything in the gas or condensed phases. Photonics, laser technology, etc. Spectroscopy- Interaction between light and matter We’re still interested in the transition dipole integral, M x21 (aka X 21 , R x21 , plus y and z analogs) which has veto power, and figures prominently in dP 21 /dt. Prob = |a 2 (t)| 2 = |  2 o | x | 1 o | 2 (E x o ) 2 2 21 ) ( ) ( ) ( 2 21 21 h E e e t h E i t h E i Prob = -2 |  2 o | x | 1 o | 2 (E x o ) 2 t For last midterm: Covered rotationally resolved vibrational transitions of diatomics, molecular symmetry, and vibrational transitions in polyatomics (direct absorption versus Raman). Use of character tables facilitates determining which transitions are allowed via which technique. 1. Rotational structure in vibrational transitions of polyatomics. See lecture 25 notes for refresher on rotational energy of polyatomics, particularly for symmetric top molecules. Recall vib (Q 1 , Q 2 , … Q i ,…, Q 3N-6 ) = (Q 1 ) (Q 2 ) (Q i ) (Q 3N-6 ) Which modes are active in IR spectroscopy? Those for which (Q i ) = ( x,y or z ) IR spectroscopy selection rules, remember that  = 1 (within the harmonic approximation, and only one mode changes at a time. However, by going beyond the simple harmonic approximation,  = 2, 3 … can be observed (though with lower intensity), and combination transitions can also be observe (  j = +1 along with  k = +1, for example) For symmetric rotor, If (Q i ) = ( z ), a vibrational transition is considered a parallel transition  i = 1 J = 0, 1 AND K = 0 when K 0
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3 J = 1 AND K = 0 when K = 0 If (Q i ) = ( x or y
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This note was uploaded on 01/18/2012 for the course C 566 taught by Professor Carolinechickjarroll during the Spring '11 term at Indiana.

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C566lecture26mt2review - Review for Midterm 2 Topics...

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