1. Spectra of dipole bound states and their role in the electron attachment in interstellar clouds Felix Güthe 1,2 1 abcd Switzerland Ltd., Baden, Switzerland 2 Institut für Physikalische Chemie der Universität Basel, Basel, Switzerland Royal Astronomical Society meeting "Polyatomics and DIBs in Diffuse Interstellar Clouds" on 8 and 9 Jan at UMIST. Thanks to : John Maier Marek Tulej M. V. Pachkov Thomas Pino

2. taken from: http://cfa-www.harvard.edu/cfa/mmw/mmwlab/ismmolecules_organic.html

3. Spectroscopic techniques Spectral range: UV/visible for DIBs Direct absorption –I/I 0 –sensitivity and selectivity –multiple passes and Cavity Ring Down Spectroscopy or Laser induced Fluorescence excited state lifetime, fluorescence quantum yield Mass selective techniques –Resonance Enhanced Multi Photon Ionisation (and related - R2ColourPhotoDetachment) –change in the m/z ratio (anion  neutral ; neutral  cation, cation  Fragment) –sensitivity for ion detection is high! –additional molecular information: mass –physics of the ionisation/detachment process is important

4. Experimental setup resonant two colour photo detachment R2CPD

5. Massspectrum of the ion source

6. Anion spectroscopy A    A +e - Photodetachment threshold

7. Dipole bound states -DBSs analogous to Rydberg states for neutrals - large orbital requires a minimum dipole moment of ~2- 2.5 Debye to bind extra electron ground state or excited state rovibrationally excited states of the DBS can be unbound M. Gutowski et al.

8. PD-Spectra of C 2n H - (n=2-4) 1   1  + transitions close to the threshold (EA). binding energies ~200 -500 cm -1 for C 4 H - DBS connected to an excited neutral state (E( 2 )> E( 2  + )) transitions in the UV (no DIBs) (<350nm)

9. Origin of C 4 H - (DBS) rotational resolution, bent upper state

10. PD-spectrum of l-C 3 H 2 - (DBS) assigned by: K. Yokoyama, Gary W. Leach, Joseph B. Kim, and W. C. Lineberger, J. Chem. Phys. 105, 10696 +10706, 1996

11. PD-spectrum with different excitation / detachment lasers Molecular beam T= ~50K bound states only visible in upper traces

12. K-structure of the two strongest vibronic bands

13. Comparison to DIBs

14. LaboratoryAstronomical Peak nmDIB (nm)fwhm (nm) EW (mÅ) A 1 699.37(7)699.32(J)0.096116 699.318(G) A 3 678.81(7)678.87(J)0.0877 678.866(W)2.3 A 4 648.97(1)649.19(J)0.07618 648.962(W)3.6 648.929(T)0.0646-12 A 5 615.21(2)615,115(T)0.1440-15 B 12 496.39(30)496.40(J)0.063 16 496.389(T)0.071 31 496.390(K) C 1 498.49(15)498.47(J)0.065 11 498,478(T)0.067 19 498.481 (K) C 3 488.74(30)488,18(J)0.13522 488,04(J)1.97611 488.256(T)1.49>466 J=Jenniskens & Desert (1994), G=Galazutdinov et al. http://www.sao.ru/~gala/DIBwavelength.htm, T= Tuairisg et al. (2000), W = Weselak et al. (2000) All bands in question are narrow only the origin band is considered strong

15. full PD-Spectrum of l-C 3 H 2 -

16. Ratio of anions to neutrals k att = electron attachment k col = collisional detachment k det = photodetachment k rec = recombinational detachment Anion abundance in diffuse interstellar clouds k f = formation rate temporary negative ion (~r -2 ) k r = radiative stabilisation (10-1000 s -1 ) k DA = dissociative association k AD = autodetachment

17. Anion abundance in diffuse interstellar clouds The capture probablity (k f ) of slow electrons by polar neutrals is high Attachment will be enhanced by rovibrational Feshbach states (“doorway states”) for fast internal conversion (IC) to the electronic ground state radiative stabilisation (k r ) can compete with autodetachment (k AD ) for slow IC the lifetime of the resonance has to be sufficiently long to compete with k AD

18. Conclusions DIB for l-C 3 H 2 - match not unlikely or disproven. Anion formation is possible for polar molecules with high EA (as detected by MW spectroscopy) DBS transitions are strong and in the vis /near UV Intensity would be only 0.5 % of all DIBs and No. 45 (in intensity) in Jennikens compilation the most intense DIBs are propably not DBS

19. Lifetime of rovibrational Feshbach states 400 cm -1 above the binding energy AD could not be observed at the threshold AD lifetimes must be longer than radiative stbilisation (k r ) K. Yokoyama, Gary W. Leach, Joseph B. Kim, and W. C. Lineberger, J. Chem. Phys. 105, 10696 +10706, 1996

20. Comparison to Yokohama et al. R2CPD 50 K our work K. Yokoyama, Gary W. Leach, Joseph B. Kim, and W. C. Lineberger, J. Chem. Phys. 105, 10696 +10706, 1996 one colour high resolution 500K

21. K. Yokoyama, Gary W. Leach, Joseph B. Kim, and W. C. Lineberger, J. Chem. Phys. 105, 10696 +10706, 1996. H 2 CCC – :discrepancy between two experiments

22. let’s compare this: p 10709 overlapping the upper and the lower graph with our data ->

23. K. Yokoyama, Gary W. Leach, Joseph B. Kim, and W. C. Lineberger, J. Chem. Phys. 105, 10696 +10706, 1996. H 2 CCC – : upper graph: ok, bu t than the frequency and the origin position in Yokoyama et al. disagree

24. K. Yokoyama, Gary W. Leach, Joseph B. Kim, and W. C. Lineberger, J. Chem. Phys. 105, 10696 +10706, 1996. H 2 CCC – :discrepancy between two experiments ?? lower graph

25. H 2 CCC – :origin K. Yokoyama, Gary W. Leach, Joseph B. Kim, and W. C. Lineberger, J. Chem. Phys. 105, 10696 +10706, 1996.

26. H 2 CCC – :discrepancy between two experiments K. Yokoyama, Gary W. Leach, Joseph B. Kim, and W. C. Lineberger, J. Chem. Phys. 105, 10696 +10706, 1996. at 14284.42 cm -1 freq. cited Iodine calibration * = estimation laboratory bandDIB (best value)coinc.? 699.37(7) 14294.6(1.5)14295.66699.32 (J)+ (s) 678.81 (7)14727.5(1.5)14726.29678.87 (J)? 648.97 (1)15404.7(0.3)15404.96648.962 (W)+ (w) 615.21 (2)16250.1 (0.5) 16252.62615.115 (T)?

27. conclusion about coincidence discrepancies: –our lab -DIB <1cm -1 –our lab -simulation Yokoyama <1cm -1 –precision of our laser (no iodine) ~1cm -1 –our spectrum overlaps with DIB –the position of the DIB has not changed from Jenniskens to McCall or Galazutdimov the two spectra from p 10709 don’t agree O° is perturbed (p. 10708- paragraph B) O° is not visible in Yokoyama -> How can McCall / Oka rule out the Match ?

28. PD-spectrum of l-C 3 H 2 - and l-C 3 D 2 - (DBS)

29. Levels of the K-structure coldest transition belongs to the 0-1 K- stack B. J. McCall, T. Oka, J. Thorburn, L. M. Hobbs, and D. G. York The Astrophysical Journal, 567:L145–L148, 2002

30. 2002 study on l-C 3 H 2 - Bands B. J. McCall, T. Oka, J. Thorburn, L. M. Hobbs, and D. G. York The Astrophysical Journal, 567:L145–L148, 2002

31. PD-spectrum of l-C 3 H 2 - and l-C 3 D 2 - ( Feshbach states )

32. end C3H2- additional material

33. Autodetaching states of C 3 - EA = 1.995eV

34. Origin band A 2  u -X 2  g Rotational profiles of the band origins Origin band B 2  u - -X 2  g life time  < 5ps

35. Autodetaching states of C 3 -

36. R2CPD spectra of the C N H - (odd)

37. R2CPD and Matrix spectra of C 2n H -

38. Two isomers of C N H - structured band for (c) only in gas phase! intensities can be differed in matrix!

39. Orgins of the C N H - anions DIB-range

41. MH - + e- MH - +h vis M - + H MH *- (TNI)  (e-), T,  (e-) f, ISRF, EA k 2,[H,H 2 ] MH -* MH - +h vis M - + H MH + e- MH - +h IR k ISC k AD k AD,vib k rad,IR k rad,vis k DA k DA,RRKM ?? Kinetics of the Anion Chemistry not included: high energetic radition, shocks, dust grain chemistry

42. Gasphase R2CPD spectrum of C 7 - Laboratory Astronomical

43. Comparison with astronomical data 1st vibronic band origin band astronomy laboratory 

44.  

45. end anions additional material