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Electronic spectr um of l-C 3 H 2 -

Photodetachment spectrum of l-C 3 H 2 - : The role of dipole bound states for electron attachment in interstellar clouds F. Güthe *1,3 , M. Tulej 2,3 , and J. P. Maier 3 1 Alstom Schweiz, Baden, Switzerland 2 Paul Scherrer Institut, Villigen, Switzerland

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Electronic spectr um of l-C 3 H 2 -

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  1. Photodetachment spectrum of l-C3H2-: The role of dipole bound states for electron attachment in interstellar clouds • F. Güthe*1,3, M. Tulej2,3, and J. P. Maier3 • 1 Alstom Schweiz, Baden, Switzerland2 Paul Scherrer Institut, Villigen, Switzerland • 3 Institut für Physikalische Chemie der Universität Basel, Basel, Switzerland • *email: felix.guethe@power.alstom.com Experimental Setup1 of the R2CPD gas phase experiment: Electronic spectrumof l-C3H2- The electronic spectrum of the linear propadienylidene anion l-C3H2- has been recorded at 50 K by resonance enhanced two photon detachment spectroscopy. This resembles the absorption spectrum to a dipole bound state involving bound-bound and bound-free transitions as well as to Feshbach states. Electronic Feshbach state Dipole bound state To explain the abundance of this carrier in interstellar clouds the ratio of anions to neutrals is estimated for small polar molecules with high electron affinities using chemical considerations. Bound states (below the detachment threshold) can only be seen if a second photon is absorbed! -> Two colour two photon detachment (R2CPD) An appreciable amount of anions can result in diffuse clouds because the electron attachment to polar molecules is enhanced via dipole bound states. • CnH Pics • experimental : 3 cases • slide • C4H to C8H • C4H to C4D HIRES • Feshbach things • general DBS things polar +e- denstiy In interstellar conditions only the K =1¬0 components should be visiblein absorption DIB comparison Laboratory Astronomical Peak nm DIB (nm) fwhm (nm) EW (mÅ) A1 699.37(7) 699.32(J) 0.096 116 699.318(G) A3678.81(7) 678.87(J) 0.087 7 678.866(W) 2.3 A4648.97(1) 649.19(J) 0.076 18 648.962(W) 3.6 648.929(T) 0.064 6-12 A5615.21(2) 615,115(T) 0.144 0-15 B12496.39(30) 496.40(J) 0.063 16 496.389(T) 0.071 31 496.390(K) C1 498.49(15) 498.47(J) 0.065 11 498,478(T) 0.067 19 498.481 (K) C3488.74(30) 488,18(J) 0.135 22 488,04(J) 1.97 611 488.256(T) 1.49 >466 • References: • Tulej, M.; Güthe, F.; Schnaiter, M.; Pachkov, M. V.; Kirkwood, D. A.; Maier, J. P.; Fischer, G. J. Phys.Chem. A 1999, 103, 9712. • Güthe, F.; Tulej, M.; Pachkov, M. P.; Maier, J. P. Astrophys. J , 555, (2001) • Yokoyama, K., Leach, G. W., Kim, J. B., & Lineberger, W. C., 1996, J. Chem. Phys., 105, 10696and 10706

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