Die Chemie des interstellaren Raumes

Abstract

Wahrend der letzten zehn bis zwanzig Jahre entdeckten Radioastronomen nahezu hundert chemische Verbindungen im Raum zwischen den Sternen, speziell

Crossed-beam reaction of carbon atoms with hydrocarbon molecules. IV. Chemical dynamics of methylpropargyl radical formation, C4H5, from reaction of C(3Pj) with propylene, C3H6 (X 1A)

“…Although neither C 3 H 6 nor C 4 H 5 have been identified in the interstellar medium ͑ISM͒ explicitly, the extraterrestrial propylene existence seems reasonable since unsubstituted C 2 H 4 was detected in the circumstellar envelope of the evolved carbon star IRCϩ10216 and the two lowest alkynes acetylene ͑C 2 H 2 ͒ and methylacetylene ͑CH 3 CCH͒ are ubiquitous in the ISM. 6 Beyond its interstellar relevance, Voyager data depict propylene in Titan's and in the upper Neptunian atmosphere. [7][8][9][10] Recent MeV and keV ion induced collision cascade simulations in hydrocarbon ices 11 as well as planetary atmospheres 12 show a production rate of, e.g., 70 suprathermal knock-on carbon atoms per impinging 12 keV carbon atom originating from the solar radiation field.…”

Chemical Evolution and the Origin of Life

“…The chemical reactions which take place under the extreme conditions of outer space are complex and not always comparable to those which can be simulated under laboratory conditions: Eric Herbst (1990) provides a survey.…”

Observing Unimolecular Dissociation of Metastable Ions in FT-ICR: A Novel Application of the Continuous Ejection Technique

“…The study of ion−molecule reactions in the gas phase has been a very active area for over two decades. − In particular, there has been an intense interest in low-pressure ion−molecule association reactions. − Ion−molecule reactions involve collisions between ions and neutral molecules to form metastable adduct ions. In the simplest case, the probability of observing stabilized adduct ions depends on the competition between back-dissociation and stabilization of the metastable adduct ions. − Metastable adduct ions can be stabilized by either photon emission or additional collisions, as expressed by reaction 1 where the rate constants are those for adduct formation ( k f ), back-dissociation ( k b ), collisional stabilization ( k c ), and radiative stabilization ( k r ) …”

“…In the low-pressure regime (∼10 -8 Torr in an ion cyclotron resonance (ICR) cell or in interstellar space), where third-body collisional stabilization of the metastable adduct ions is very slow, the metastable ions are stabilized predominantly by emitting infrared photons, a process termed radiative association (RA). , The role of radiative association reactions in the chemistry of interstellar clouds has long received a great deal of attention by astrochemists and astrophysicists. − It is believed that radiative association is an important route in building large molecules and ions in the interstellar environment.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] In particular, there has been an intense interest in low-pressure ion-molecule association reactions. [14][15][16][17][18][19][20][21][22][23] Ion-molecule reactions involve collisions between ions and neutral molecules to form metastable adduct ions. In the simplest case, the probability of observing stabilized adduct ions depends on the competition between backdissociation and stabilization of the metastable adduct ions.…”