Overtone Transition 2ν of HCO and HOC: Origin, Radiative Lifetime, Collisional Quenching.

We present spectra of the first overtone vibration transition of C-H/ O-H stretch (2ν) in HCO and HOC, recorded using a laser induced reaction action scheme inside a cryogenic 22 pole radio frequency trap. Band origins have been located at 6078.68411(19) and 6360.

Measurements of rate coefficients of CN+, HCN+, and HNC+ collisions with H2 at cryogenic temperatures.

The experimental determination of the reaction rate coefficients for production and destruction of HCN+ and HNC+ in collision with H2 is presented. A variable-temperature, 22-pole radio frequency ion trap was used to study the reactions in the temperature range 17-250 K. The obtained rate coefficients for the reaction of CN+ and HCN+ with H2 are close to the collisional (Langevin) value, whereas that for the reaction of HNC+ with H2 is quickly decreasing with increasing temperature.

Four annular structures in a protostellar disk less than 500,000 years old.

Annular structures (rings and gaps) in disks around pre-main-sequence stars have been detected in abundance towards class II protostellar objects that are approximately 1,000,000 years old. These structures are often interpreted as evidence of planet formation, with planetary-mass bodies carving rings and gaps in the disk. This implies that planet formation may already be underway in even younger disks in the class I phase, when the protostar is still embedded in a larger-scale dense envelope of gas and dust.

State-to-State Rate Coefficients for NH-NH Collisions from Pump-Probe Chirped Pulse Experiments.

The kinetics of rotational inelastic NH-NH collisions are recorded using pump-probe experiments, carried out with a K-band waveguide chirped pulse Fourier transform microwave spectrometer, in which the population of one inversion doublet is altered by the pump pulse. Due to self-collisions, the resulting deviation from equilibrium propagates to other states and, thus, can be interrogated by probe pulses as a function of the pump-probe delay time. A clear hierarchy of the state-to-state collision processes is found and subsequently translated into propensity rules.

The Spatial Distribution of Complex Organic Molecules in the L1544 Pre-stellar Core.

The detection of complex organic molecules (COMs) toward cold sources such as pre-stellar cores (with T<10 K), has challenged our understanding of the formation processes of COMs in the interstellar medium. Recent modelling on COM chemistry at low temperatures has provided new insight into these processes predicting that COM formation depends strongly on parameters such as visual extinction and the level of CO freeze out. We report deep observations of COMs toward two positions in the L1544 pre-stellar core: the dense, highly-extinguished continuum peak with A ≥30 mag within the inner 2700 au; and a low-density shell with average A ~7.

The formation of a quadruple star system with wide separation.

The initial multiplicity of stellar systems is highly uncertain. A number of mechanisms have been proposed to explain the origin of binary and multiple star systems, including core fragmentation, disk fragmentation and stellar capture. Observations show that protostellar and pre-main-sequence multiplicity is higher than the multiplicity found in field stars, which suggests that dynamical interactions occur early, splitting up multiple systems and modifying the initial stellar separations.

H2D(+) observations give an age of at least one million years for a cloud core forming Sun-like stars.

The age of dense interstellar cloud cores, where stars and planets form, is a crucial parameter in star formation and difficult to measure. Some models predict rapid collapse, whereas others predict timescales of more than one million years (ref. 3).

Are gas-phase models of interstellar chemistry tenable? The case of methanol.

We consider the case of methanol production in cold dark clouds, also known as quiescent cores, for which recent work shows that a purely gas-phase synthesis is unlikely to produce a sufficient amount to explain the observational fractional abundance of approximately 10(-9). Moreover, recent experiments appear to confirm a previous hypothesis that methanol can be formed on cold grain surfaces by the hydrogenation of CO via successive reactions with hydrogen atoms. In this paper we consider two ways of including the surface formation of methanol into chemical models of cold dark clouds.