Nonthermal Chemistry Induced by Visible Light H. Floyd Davis - PowerPoint PPT Presentation

Nonthermal Chemistry Induced by Visible Light H. Floyd Davis Department of Chemistry and Chemical Biology Cornell University 1

Reactions of Triplet Diacetylene HCCCCH 2

Reactions of Triplet Diacetylene HCCCCH Zwier Group, Purdue 3

Photoinduced Reactivity of Diacetylene, C 4 H 2 Zwier, Science 258, 1630 (1992) 4

Spectrum of Solar Radiation on Titan 5

Vibrational Levels of Molecules Infrared Absorption e.g., C-H stretch V = 0 → 1 6

Vibrational Levels of Molecules First Overtone excitation (v = 0 →2) 7

Vibrational Levels of Molecules Fourth Overtone excitation (v = 0 →5) 8

Why is the ocean blue? Due to OH Overtone Absorption of red light 9

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Calculated Singlet C 4 H 4 Energetics Mebel, J. Chem. Phys. 125, 133113 (2006) Calculated singlet C 4 H 4 energetics (kJ/mol) Addition barrier is 140 kJ/mol. Corresponds to photon at 856 nm 11

Spectrum of Solar Radiation on Titan C 2 H 2 v = 0 →5 band at 640 nm 12

Acetylene 5 v CH Photoacoustic Spectrum 13

Acetylene 4 v CH Overtone Spectrum (787 nm): Room Temp vs. Molecular Beam . Room T Low T 14

Pulsed Valve/Flow Reactor Laser 15

VUV Photoionization TOF Apparatus 16

Absorption Spectra of Polyenes Christensen, J. Phys. Chem. A 117, 1449 (2013) 17

Electronic Excitation Energies of Polyenes Decrease with number of monomer units, N “1D particle in a box” 18

What about HCN Polymerization? 19

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Acknowledgements: Jonathan Lunine David Shalloway David Usher 21

Polyene Photochemistry (Kohler) 22

Nonreactive Scattering of C 2 H 2 (v) with other molecules 23

Polymerization of Acetylene? 24

UV Excitation Produces Triplet Acetylene J. Chem. Phys 106, 5292 (1997) No triplets formed above 5.86 eV: Due to onset of photodissociation 25

Zwier, Science 258, 1630 (1992) Laser on Laser off Difference 26

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