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Jet cooled Laser Induced Fluorescence Spectroscopy of FCH 2 CH 2 O and other photo-fragments of XCH 2 CH 2 ONO (X=F,Cl,Br,OH) Rabi Chhantyal-Pun, Ming-Wei.

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Presentation on theme: "Jet cooled Laser Induced Fluorescence Spectroscopy of FCH 2 CH 2 O and other photo-fragments of XCH 2 CH 2 ONO (X=F,Cl,Br,OH) Rabi Chhantyal-Pun, Ming-Wei."— Presentation transcript:

1 Jet cooled Laser Induced Fluorescence Spectroscopy of FCH 2 CH 2 O and other photo-fragments of XCH 2 CH 2 ONO (X=F,Cl,Br,OH) Rabi Chhantyal-Pun, Ming-Wei Chen, Terry A. Miller

2 Motivation OH substituted alkoxy radicals are important intermediate in atmospheric oxidation of alkenes like Ethene, Butadiene and Isoprene HOCH 2 CH 2 O radical is produced from OH initiated oxidation of Ethene Halogen substituted Ethoxy can be a model for the study of HOCH 2 CH 2 O radical S. Sawada and T. Totsuka, Atmos. Environ. 20, 821 (1986)

3 Spectroscopy of Alkoxy radicals ~~ Laser Induced Fluorescence (LIF) method has been used in the past to study the B-X transition of alkoxy radicals LIF coupled with Supersonic free jet expansion produces rotationally cold spectrum; rotational contours (obtained even with moderate resolution) can then be used to differentiate different conformers 1-Propoxy Gapolakrishnan S. PhD thesis The Ohio State University, 2003

4 XCH 2 CH 2 ONO / He General Valve ControllerDG535 Pulse Generator XeF Excimer Laser Nd:YAG Laser Sirah Dye Laser Nozzle T0T0 PMT Q-Switch Flash Lamp T 0 / GPIB T0T0 Lens Frequency Doubler Precursor preperation: XCH 2 CH 2 OH/H 2 SO 4 /NaNO 2 Experimental apparatus XCH 2 CH 2 O NO

5 LIF survey scan of Photo-Fragments of FCH 2 CH 2 ONO HCHO

6 G and T conformers of FEO Gauche (G)Trans (T) -Rotational constants were obtained from hf/6-31+g* and ucis/6-31+g* -TDMs were obtained from Ethoxy exp.

7 Assignment of the Origin bands 000000 000000 HCHO 1 Gopalakrishnan et. al J. Chem. Phys. 118 (2003) 49–54 AlkoxyExp. 1-Propoxy G 1 28634 1-Propoxt T 1 29219 FEO-G 29869 FEO-T 30519

8 TG 1.53 1.38 108.2 113.6 1.49 1.51 108.2 109.5 104.0 111.7 105.3 108.4 1.53 1.38 1.51 1.52 X and B state geometries -UCIS/6-31+G(D) HF/6-31+G(D) 76.O 70.0 OCCF dihedral ~~ All angles are in degrees and bond lengths are in Å

9 1 ucis/6-31+g(d) 2 Tarcazy et.al. J. Mol. Spec. 220 (2003) 276–29 ModeExp.Calc. 1 Description 17256300Asym CCO/ CCF bend 16513476Sym CCO/CCF bend 14699903CO stretch 18149160CC torsion 17324358Sym CCO/CCF bend 15604832CO stretch ConformerPropoxy CO str.FEO Co str. Exp.0.76XCalc. 2 Exp.0.79XCalc. 2 G596590604632 T676642699686

10 ClCH 2 CH 2 ONO / FCH 2 CH 2 ONO 1 Gopalakrishnan et. al J. Chem. Phys. 118 (2003) 49–54 HCHO 28786? AlkoxyCO str. Ethoxy603 Prpoxy-G596 FEO-G604 546 AlkoxyExp. 1-Propoxy G 1 28634 1-Propoxt T 1 29219 FEO-G 29869 FEO-T 30519 ClEO-G ClEO-T

11 -Vinoxy spectrum Brock et. al. JCP 106 10048

12 Verification of hot bands

13 Assignment of Hot bands of Vinoxy 1 Brock et. al. JCP 106(24) 10048 1997 ModeDescriptionX1X1 B1B1 X-BExp. 9CCO bend5004495151.3 12CC torsion404274130127.7

14 CH 2 CHO from other XCH 2 CH 2 ONO (X=OH,Cl,F,Br)

15 Conclusion Obtained and analyzed the Laser Induced Fluorescence spectrum of B-X transition of FEO radical CH 2 CHO and HCHO fragments are produced following the photodissociation of XCH 2 CH 2 ONO (X= OH, F, Cl, Br) Analysis of the mechanism for the formation of CH 2 CHO is going on ~~

16 Acknowledgement Professor Terry Miller (advisor) Miller group members Dr. Dmitry Melnik Dr. Jin Jun Liu Neal Kline Terrance Codd DOE for funding

17 Possible mechanism


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