71 st International Symposium on Molecular Spectroscopy Photodissociation dynamics of N contaning heterocyclic molecules; pyridine and isoxazole studied using chirped pulse uniform flow spectroscopy This study had been started in our lab back in Wayne state university and continued at university of missouri. Nuwandi M. Ariyasingha University of Missouri Columbia

Pyridine Isoxazole Agrochemical and pharmacological applications 71 st International Symposium on Molecular Spectroscopy Pyridine Isoxazole Agrochemical and pharmacological applications N containing building blocks of PAH Volatile Vapor pressure ~ 18 mmHg and ~ 97 mmHg for pyridine and isoxazole respectively Direct photolysis Adverse health effects

C5NH5→ C5NH4 + H ; direct dissociation (10%) C5NH5→ C4H4 + HCN Previous studies 71 st International Symposium on Molecular Spectroscopy A multi-mass ion imaging study done by Chi-Kung Ni , Y T Lee and Alex Mebel in 2005 C5NH5→ C5NH4 + H ; direct dissociation (10%) C5NH5→ C4H4 + HCN C5NH5 → C3H3 + C2NH2 C5NH5 → C2H4 + C3NH C5NH5 → C4NH2 + CH3 (14%) C5NH5 → C2H2 + C3NH3 ring opening channels Lin. M.F.; Dyakov. Y.A.; Tseng. C.M.; Mebel. A.M.; Lin. S.H.; Lee. Y.T.; Ni. C.K. J. Chem. Phys. 2005, 123, 054309.

Instrumentation and Method 71 st International Symposium on Molecular Spectroscopy Instrumentation and Method Chirped Pulsed FTMW Pulsed Uniform Supersonic Flow system High density flows (1016 cm-3) Uniform, collimated flows Constant pressure Temperature (22K/26K) CPUF

Chirped Pulse in Uniform Flow (CPUF) 71 st International Symposium on Molecular Spectroscopy Chirped Pulse in Uniform Flow (CPUF)

71 st International Symposium on Molecular Spectroscopy Results 1.

71 st International Symposium on Molecular Spectroscopy t = 10 µs t = 20 µs t = 30 µs t = 40 µs t = 50 µs t = 60 µs t = 70 µs t = 80 µs t = 90 µs t = 100 µs t = 120 µs t = 110 µs Frequency / GHz HCN J= 1-0 2.

71 st International Symposium on Molecular Spectroscopy 3.

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71 st International Symposium on Molecular Spectroscopy 5. MITC frames 1 to 12 laser on 100 k aquisitions

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Results By Alexander Mebel o: m:p = 36:5:4 .0012 11.8 1.8 HC3N at 81.881 GHz HC3N at 82.627 GHz Each spectrum is averaged for 125 k 1.8 By Alexander Mebel

Calculated Branching using CPUF HCN : HNC 8 : 1 71 st International Symposium on Molecular Spectroscopy However, Calculated Branching using CPUF HCN : HNC 8 : 1 In theory HCN : HNC 11 : 0.0001

71 st International Symposium on Molecular Spectroscopy 7.

71 st International Symposium on Molecular Spectroscopy Estimated branching (%) RRKM MESS calculations HCN + C4H4 11 21 HNC + C4H4  1E-04 8E-05 C2H2 + C2H3CN 6E-03 2E-03 C2H4 + HCCCN 2 1E-01 o-C5H4N + H  36 15 m-C5H4N + H 5 p-C5H4N + H  4 CH3 + HC3HCN 35 i1  3 i17 31 i18  5E-01 i21 i26  7E-02 By Alexander Mebel

Results Isomerization !! By Alexander Mebel .0012 11.8 HC3N at 81.881 GHz HC3N at 82.627 GHz Each spectrum is averaged for 125 k By Alexander Mebel

71 st International Symposium on Molecular Spectroscopy Discussion HCN can be produced hot. Excess energy ~ 82 kcal/mol distributed between translational and internal energies of fragments. Hot HCN isomerizes to HNC. Hot distribution branching ratios; Well  E, kcal/mol       HCN     HNC HCN       60.              0.52     0.47 HCN      50.               0.60     0.39 HCN      40.               0.65     0.34 HCN      39.               0.66     0.33 HCN      38.               0.66     0.33 HCN      37.               0.66     0.33 HCN      36.               0.67     0.32 HCN      35.               0.67     0.32 HCN      34.               0.68     0.31 HCN      33.               0.74     0.25 HCN      32.               0.88     0.11 HCN      31.               0.99   0.006

Isoxazole photodissociation at 248 nm: preliminary results 71 st International Symposium on Molecular Spectroscopy Isoxazole photodissociation at 248 nm: preliminary results

71 st International Symposium on Molecular Spectroscopy Acknowledgement Prof. Arthur Suits (MIZZOU) Prof. Alexander Mebel (FIU) Dr. Baptiste Joalland (RENNES) C-PUF Team Former members Dr. Lindsay Zack Dr. Chamara Abeysekara Suits Group Members DOE & NSF

71 st International Symposium on Molecular Spectroscopy Thank You

fragment transnational energy distributions of the reactions C5NH5→C3NH +C2H4 and C5NH5→C4H4+HCN show that the maximum transnational energies reach the maximum available energies of these reactions. Since the maximum transnational energy corresponds to the products produced in the ground electronic state and the ground states of these closed-shell fragments only correlate to the ground state of the parent molecule, the dissociation must occur in the ground electronic state