Hydrated sulphuric acid in dense molecular clouds

We consider sulphur depletion in dense molecular clouds, and suggest hydrated sulphuric acid, H2SO4 · nH2O, as a component of interstellar dust in icy mantles. We discuss the formation of hydrated sulphuric acid in collapsing clouds and its instability in heated regions in terms of the existing hot core models and observations. We also show that some features of the infrared spectrum of hydrated sulphuric acid have correspondence in the observed spectra of young stellar objects.Physic

The Chemical Age of the Bok Globule CB238

The Bok globule CB238 has been investigated in 13CO (220.4 GHz), C18O (109.7 GHz), CS (97.9 and 146.7 GHz), and SO (99.3 GHz) lines, and mapped with half-power beamwidths of 11'', 22'', 38'', 16'', and 36'', respectively. The two dense cores previously found in NH3 are presently confirmed in CS. The cores exhibit similar physical and chemical characteristics. The lack of outflows, the limited chemical content, and the very modest depletion in the ammonia cores provide evidence that CB238 is not an evolved object. Molecular abundances and density ratios constrain chemical modeling whose results provide a chemical age close to the free-fall timescale

H 2 O-H 2 O Collision Rate Coefficients

H2O-H2O collision cross sections are calculated by adapting the method developed by Anderson and Tsao and Cornette for the calculation of collision broadening of molecular spectral lines. Cross sections are computed with a cutoff limit at 20 A2 for the rotational levels of water with J ≤ 10 and E < 2000 cm-1 in the temperature range 100-800 K. The accuracy of the calculated values is estimated to be 10%-20%

Role of clays in protecting adsorbed DNA against X-ray radiation

The X-ray emission of the young Sun was much harder and intense than today and might have played a significant role in the evolution of complex organics in protoplanetary environments. We investigate the effects of soft X-rays on tryptophan molecules in aqueous solutions at room temperature. As results of the irradiation experiments we detect several light species indicative of fragmentation, together with large molecular structures such as tryptophan dipeptide and tripeptide. Complexification is more evident in H2O solution than in D2O, probably due to isotopic effects. The abundances of peptides depend on the irradiation dose and decrease with increasing energy deposition. Radicals such as D, OD, H and OH, induced by the X-ray interaction with solvents, play a major role in determining the final products