1. ERIC HERBST DEPARTMENTS OF PHYSICS, CHEMISTRY AND ASTRONOMY THE OHIO STATE UNIVERSITY Gaseous Chemistry in Interstellar Space

2. Molecules seen in UV,visible, & IR absorption Diffuse Matter

5. A GIANT CLOUD

6. TMC-1 in CCS

12. MOLECULAR ROTATION “radio” emissions  E = h

16. MOLECULAR VIBRATIONS Infrared absorption

20. Cosmic rays produce ions

21. Radical-Neutral Reactions Radicals: C, CN, CCH 1) Inverse T dependence 2) Large rate coefficients by 10-50 K: k ~ 10(-10) cm 3 s -1

22. FORMATION OF GASEOUS WATER H 2 + COSMIC RAYS  H 2 + + e Elemental abundances: C,O,N = 10(-4); C<O H 2 + + H 2  H 3 + + H H 3 + + O  OH + + H 2 OH n + + H 2  OH n+1 + + H H 3 O + + e  H 2 O + H; OH + 2H, etc

23. FORMATION OF HYDROCARBONS H 3 + + C  CH + + H 2 CH n + + H 2  CH n+1 + + H; n=1,2 CH 3 + + H 2  CH 5 + + h CH 5 + + e  CH 4 + H (5%)  CH 3 + 2H (70%) CH 5 + + CO  CH 4 + HCO +

25. FORMATION OF O 2,N 2 CO OH + O  O 2 + H OH + N  NO + H NO + N  N 2 + O CO, N 2 + He +  C +, N + +… Precursor to ammonia, hydrocarbons CH + O  CO + H

27. Latest network – osu.2003 – contains over 300 rapid neutral-neutral reactions. Rate coefficients estimated by Ian Smith and others. Deuteration requires networks twice as large!!! Other networks: nsm, Rate99

28. At earlier times, abundances for many small species close to steady state values.

29. Steady-state analysis of H 3 +

30. Steady-state analysis of H 2 D + Actually, D/H abundance ratios less time-dependent than actual concentrations in absence of accretion.

31. Deuterium Fractionation Species Fractionation Model NH 2 D 0.0110.020 HDCO0.0590.055 DCN0.0110.025 DCO + 0.020.062 N 2 D + 0.080.052 CH 3 OD0.0270.030

32. Agreement with TMC-1 nsm

33. Source of Difficulty Rapid neutral-neutral reactions not studied in the laboratory; for example, O + C 3  CO + C 2 ????? C + C 3  C 4 + h ?????

34. TMC-1 Gas-grain models with nsm