Laser spectroscopy of extraterrestrial molecules
As the last embers of a red giant star die down, it undergoes a series of expansions and contractions, puffing away the outer layers of the star, resulting in the expulsion of its carbon rich atmosphere into the cosmos. As the central stellar core contracts under gravity into a white dwarf, the atmosphere evolves into a nascent proto-planetary nebula, rich in carbon, oxygen, nitrogen (e.g. The Red Rectangle Fig. 1). Such a dignified end to the life of an intermediate mass star, such as our own Sun is in sharp contrast to the violent end encountered by higher mass stars which end their lives in supernova explosions. 
The chemistry of interstellar space is different to that performed in a conical flask. It is slow, driven by ion-molecule and neutral-radical reactions in the gas phase and on the surfaces of dust grains, and is highly exotic. There are a number of chemical models of interstellar space. Of note are the "UMIST gas-phase chemical network" of Millar and co-workers in Manchester and the "New Standard Model" of Herbst and co-workers in Columbus (NSM). Both these models use complicated networks of kinetic equations to model the chemistry of various interstellar environments. However, these models may only be tested by spectroscopic observation of the relative abundances of interstellar molecules, which is a field unto itself.
To understand the chemistry of interstellar clouds and nebulae one must begin by first identifying the molecules therein. It is one of Nature's greatest challenges to remotely identify the menagerie of molecules extant in the interstellar medium (ISM). Molecules are identified in the interstellar regions by their spectroscopic signatures in the millimetre, infrared and optical regions of the electromagnetic spectrum. While it is the millimetre region (radio-astronomy) which has most greatly illuminated our understanding of the structures of interstellar molecules, this technique is blind to a family of molecules of interest: those without strong permanent dipole moments. For this reason, the UMIST and NSM models concentrate on reproducing the observed abundances of polar molecules.
The infrared region features emission corresponding to specific functional groups and bonds comprising interstellar molecules. Of particular note are the 3.3 mm emission lines which are thought to originate from polycyclic aromatic hydrocarbons (PAHs), a class of molecule characterized by conjoined "benzene ring" moieties. 
Unfortunately this is hard to prove since the C-H stretching regions of the infrared spectrum corresponding to PAHs are so closely packed. Nevertheless the belief is widely held that PAHs are of great importance to understanding interstellar chemistry: the carriers of these bands are thought to comprise as much as 20% of cosmic carbon. It is in the optical regions of the electromagnetic spectrum (300-1000 nm) that there is much to be done. Despite the optical region being the part of the electromagnetic spectrum originally accessed by astronomers, there have been scarce new identifications of interstellar molecules by their electronic spectra. Two unsolved problems representing paradigms for the optical spectroscopy of interstellar molecules are that of the Diffuse Interstellar Bands (DIBs) and the Red Rectangle Bands (RRBs). The former is a collection of some 300 diffuse molecular absorption bands observed in the light of stars occluded by diffuse molecular clouds. The latter is the puzzling red emission spectrum of a nearby, carbon-rich proto-planetary nebula (Fig. 1). The two problems are intrinsically linked: The Red Rectangle is the brightest emitter of 3.3mm radiation in the sky, thereby implicating PAHs, which are also among the leading candidates for carriers of the DIBs. Additionally, the 5797 DIB has been proposed as arising from the same molecular carrier as the 5800 Angstrom RRB (see Fig. 2).
It is our aim to identify the carriers of these bands, solving the longest standing problem in molecular spectroscopy, identifying the repositories of cosmic carbon and providing an invaluable "foot in the door" to understanding extraterrestrial chemistry.
T.W. Schmidt and R.G. Sharp, The Optical Spectroscopy of Extraterrestrial Molecules. Aust. J. Chem. 2005, 58, pp 69-81.
R.G. Sharp, N.J. Reilly, S.H. Kable and T.W. Schmidt, Sequence structure emmision in the Red Rectangle Bands, Astrophys. J., 2006. 639, 194-203
N.J. Reilly, G.C. Cupitt, S.H. Kable and T.W. Schmidt, An experimental and theoretical investigation of the dispersed fluorescence spectroscopy of HC4S, J. Chem. Phys. 2006, 19, 194310