When electrons meet molecular ions and what happens next: Dissociative recombination from interstellar molecular clouds to internal combustion engines

Abstract

The interaction of matter with its environment is the driving force behind the evolution of 99% of the observed matter in the universe. The majority of the visible universe exists in a state of weak ionization, the so called fourth state of matter: plasma. Plasmas are ubiquitous, from those occurring naturally; interstellar molecular clouds, cometary comae, circumstellar shells, to those which are anthropic in origin; flames, combustion engines and fusion reactors. The evolution of these plasmas is driven by the interaction of the plasma constituents, the ions, and the electrons. One of the most important subsets of these reactions is electron-molecular ion recombination. This process is significant for two very important reasons. It is an ionization reducing reaction, removing two ionised species and producing neutral products. Furthermore, these products may themselves be reactive radical species which can then further drive the evolution of the plasma. The rate at which the electron reacts with the ion depends on many parameters, for examples the collision energy, the internal energy of the ion, and the structure of the ion itself. Measuring these properties together with the manner in which the system breaks up is therefore critical if the evolution of the environment is to be understood at all. Several techniques have been developed to study just such reactions to obtain the necessary information on the parameters. In this paper the focus will be on one the most recently developed of these, the Ion Storage Ring, together with the detection tools and techniques used to extract the necessary information from the reaction.

Experimental studies of the dissociative recombination processes for the dimethyl ether ions CD3OCD$_{2}^{+}$ and (CD3)2OD+

“…For a two-body breakup channel this can be solved analytically. For the three-body breakup case a similar approach as Müller & Cosby (1999), Thomas (2008) and Zhaunerchyk (2008) was used. For each reaction channel a large amount of DR events were numerically simulated where the energy distribution as well as the direction of the outgoing fragments are randomized (fulfilling energy and momentum conservation laws).…”

“…The phenomenon is one of the dominating ion processes in dark interstellar clouds (Boger & Sternberg 2006;Florescu-Mitchell & Mitchell 2006;Thomas 2008), the comae of comets (Haider & Bhardwaj 2005), and also plays an important role in aurorae (Peterson et al 1994), aeronomical plasmas (Yee et al 1989), lightning (Smirnova et al 2002) as well as in man-made plasmas such as those in combustion processes and fusion reactors (Florescu-Mitchell & Mitchell 2006). DR is known to be very efficient at low temperatures and therefore the reaction rates involved have a significant impact on model calculations of interstellar chemistry.…”

“…The heavy-ion storage ring CRYRING in Stockholm, Sweden is an appropriate tool for investigations of astrophysically relevant DR reactions and has proven successful in doing so for several years, see e.g. Larsson et al (1993Larsson et al ( , 1995; Al-Khalili et al (1998); Neau et al (2000); McCall et al (2003); Hamberg et al (2005); Geppert et al (2005); Thomas (2008).…”

DESIREE: Physics with cold stored ion beams

“…for examples in studies of Dissociative Recombination [13,14], the platforms have been designed to accommodate a suite of different ion sources ranging from an expansion source for producing rotationally cooled molecular ions (see e.g. [15]), an electrospray source for creating biomolecules and large molecular cluster ions, and a sputter source for generating negative ions (see e.g.…”

“…In the gas phase two such neutralization processes exist: Electron-cation dissociative recombination (DR) and cation/anion mutual neutralization (MN). One of the primary motivations for the studies at CRYRING of DR for astrophysically abundant cations [13,14] has been the role of this process in interstellar chemistry in regions where the negative charge is primarily in the form of free electrons. One of the most recent observations in the interstellar medium has been that of long carbon-chain anions, the first of these only unambiguously identified less than 10 years ago [21].…”