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Research lecture
Mats LarssonStockholm University
The discovery of interstellar anions: C6H−, C4H−, C3H−, C8H−, C5H−, CN−
The new results from Herschel Space ObservatoryThe importance of H− for formation of molecules in
the Early UniverseResults from the Cassini‐Huygens space mission to
Titan, the largest moon of SaturnIdentification of H2CCC as a diffuse interstellar band
carrier (honest but probably failed attempt)Results on dissociative recombination of HCO+
The presence of anions in the interstellar medium has been discussed for a long timeLong carbon chains have many vibrational degrees
of freedomThese vibrations can accommodate excess energy
when an electrons sticks to the carbon chainLaboratory microwave spectroscopy has been
important for the discovery of interstellar anionsPat Thaddeus group at Harvard University
Department of Astronomy is at the forefront of thistype of spectroscopy
Thaddeus et al. Astrophys. J. 677, 1132 (2008)
Astrophys. J. Lett. 664, L43 (2007)
Interstellar cloud TMC‐1
Its electronic spectrum discovered by Herzberg and Lagerqvist in 1968
C2 has been observed in diffuse clouds in the visible region
Is it possible to observe C2− ?
Formation by electron radiative attachment:
X + e → X−+ hν
Destruction by:
X−+ hν→ X + e (photodetachment)
H + H−→ H2 + e (associative detachment; EarlyUniverse
H+ + H−→ 2H (mutual neutralization)
Ion trap fromRoland Wester’sLaboratory in Innsbruck
Photodetachment
Absolute cross section measured by Wester et al. in anion trap, JCP 130 061105 (2009); 5 % accuracy!
O−+ hν→ O + e
Double ElectroStatic Ion Ring ExperimEnt: DESIREE
To be commissioned late 2011, with location in Stockholm
Largest space telescope ever launched (3.5 m)It covers the wavelength range 55‐671 μmBridges the gap between earlier infrared space
missions and ground‐based radioastronomy
It is remarkable that by observing the universe in a new wavelength window, which was closed to us before Herschel, we obtain a lot of new, very exciting information
Astron. Astrophys. 518, L110 (2010)
Strong support of the gas‐phase route towater
B Larsson et al., Astron. Astrophys. 2008
August 1, 2011. Molecular oxygen detected in the Orion Nebula
No grains for formation of H2
H + H−→ H2 + e
When the Universe had cooled to about z = 100, H−was no longer destroyed by photodetachment
Kreckel, Savin et al., Science 329, 69 (2010)
Results
In the 1920s and 1930s a number of diffuse bands were discovered in addition tothe sharp atomic absorption lines
C C CH
H
Comparison laboratory and astronomical spectrum
John Maier et al. have made an honest attempt and found several bands of l‐C3H2 to coincide with some of the Diffuse Interstellar BandsThere are problems with the column density, and
the community is not convincedThe jury is still out, howeverJohn Maier is so far ahead of anyone else, so who
will enter this area?For sure, young spectroscopists do not want to
spend their careers on the DIB
HCO+ is second only to H3+ in astrophysical importanceH3+ will have its third Royal Society Discussion Meeting
in 2012, HCO+ still waits for its firstThe discovery of interstellar HCO+ triggered the
development of gas‐phase ion chemistry as a model for molecule formation in interstellar space (Klemperer, Herbst, Watson, Dalgarno)Theoretical work on HCO+ has a long history of
controversies. Experiments during 30 years in goodagreement.We have studied HCO+ in CRYRINGHCO+ + e →H + CO
Manne Siegbahn Laboratory
52 meters circumference
CO (X 1Σ+) + H 46%CO (a 3Π) + H 20%CO (a’ 3Σ+) + H 34%
FAIR, Darmstadt
2011
Future
ALMA – soon entering an Early science phase
ALMA will generate a lot of new molecular data
Who will do the corresponding laboratory work?
The reaction dynamics of anions needs to be investigated
Richard Thomas
WolfGeppert
Vitali ZhaunerchykMagdalena KaminskaErik VigrenMathias HambergIryna KashperkaMagnus af Ugglas