A new technique for determining the refractive index of ices at cryogenic temperatures.

A reflection-absorption optical (RAO) spectrometer, operating across the ultra-violet/visible (UV/visible) wavelength region, has been developed that allows simultaneous measurements of optical properties and thickness of thin solid films at cryogenic temperatures in ultrahigh vacuum. The RAO spectrometer enables such measurements to be made after ice deposition, as opposed to most current approaches which make measurements during deposition. This allows changes in the optical properties and in the thickness of the film to be determined subsequent to thermal, photon or charged particle processing.

A TPD and RAIRS comparison of the low temperature surface behavior of benzene, toluene, and xylene on graphite.

The first comparative study of the surface behavior of four small aromatic molecules, benzene, toluene, -xylene, and -xylene, adsorbed on graphite at temperatures ≤30 K, is presented. Intermolecular interactions are shown to be important in determining the growth of the molecules on the graphite surface at low (monolayer) exposures. Repulsive intermolecular interactions dominate the behavior of benzene and toluene.

Peeling the astronomical onion.

Water ice is the most abundant solid in the Universe. Understanding the formation, structure and multiplicity of physicochemical roles for water ice in the cold, dense interstellar environments in which it is predominantly observed is a crucial quest for astrochemistry as these are regions active in star and planet formation. Intuitively, we would expect the mobility of water molecules deposited or synthesised on dust grain surfaces at temperatures below 50 K to be very limited.

Gas-phase kinetics of the N + C2N reaction at low temperature.

The rate of the gas-phase N((4)S) + C2N(X(2)Πi) reaction has been measured in a continuous supersonic flow reactor down to 54 K through the relative-rate method using the N((4)S) + OH(X(2)Π) → H((2)S) + NO(X(2)Π) reaction as a reference. The microwave discharge technique was employed to produce high concentrations of atomic nitrogen. Pulsed laser photolysis of precursor molecules Cl3C2N and H2O2 at 212 nm in situ led to C2N and OH radical formation, respectively.