Laboratory astrochemistry: studying molecules under inter- and circumstellar conditions

Abstract

In this paper, we outline recent developments in and the growing need for laboratory astrochemical measurements. After a short review on experimental methods, we focus primarily upon the utility of multi-electrode ion trapping methods for addressing key problems in reaction dynamics and their applications towards gaining a better understanding of the physicochemical driving forces behind compositional development in interstellar and circumstellar environments. Temperature variable trapping techniques, combined with lasers and molecular beams are unique tools for studying state specific reactions, for ion spectroscopy and for investigating the structure and stability of complex charged objects as a function of their internal energy. Particular emphasis is given to reactions with hydrogen atoms and molecules, H-D exchange leading to isotopic fractionation, problems in hydrocarbon ion chemistry and association chemistry in rarefied environments. In the outlook, we discuss the future needs in astrochemistry in order to pave the way towards understanding the next generation of sophisticated astronomical observations and to prepare for them.

Observation of enhanced rate coefficients in the H2++H2→H3++H reaction at low collision energies

“…Studies of chemical processes involving ions at low temperature are motivated in part by the need to understand and model chemical reaction cycles in interstellar molecular clouds [6][7][8][9], which are characterized, depending on the nature of the cloud, by temperatures down to the cosmic background temperature of 2.7 K. They are also motivated by the desire to explore the regime of cold and ultracold chemistry where the reactivity is influenced by quantum phenomena [10][11][12][13][14].…”

Method for traveling-wave deceleration of buffer-gas beams of CH

“…There are several applications of intense molecular beams, from experiments attempting to measure the electron's electric dipole moment [3,4] and variation of fundamental constants [5], to experiments exploring cold reactions relevant to interstellar cloud chemistry [6]. In most of these experiments, removing the mean forward velocity is critical to taking full advantage of the molecular source.…”

Radiofrequency multipole traps: tools for spectroscopy and dynamics of cold molecular ions

“…Ref. [36,38,37,43,14]). In these experiments buffer gas cooling of the translational and internal degrees of freedom of the trapped ions provides the initial conditions for the chemical reactions.…”

“…Since then major developments have happened, most notably the introduction of the widely used 22-pole ion trap [37]. More recently, a few overview articles have reviewed multipole ion traps [41,42] and their application in mass spectrometry [7] and astrophysics [43,14].…”