Mercapto radical (SH) in translucent interstellar clouds

Hydrocarbons in diffuse and translucent clouds

We investigate the consequences on hydrocarbon chemistry in diffuse and translucent clouds of including an interaction between gaseous C+ ions and dust grains. In general, we find that models in which much of the carbon is deposited and retained on grain surfaces within the cloud lifetime represent a poor match to observations. Conversely, models in which carbon is efficiently converted to meth...

Enigma of H3 + in Diffuse Interstellar Clouds

1. INTRODUCTION H 3 + is of fundamental importance to interstellar chemistry both because it is a hydrogenic species (and >90% of all nuclei in the universe are hydrogen nuclei; see Figure 1) and because it serves as the universal protonator, initiating a chain of ion-neutral reactions that is responsible for the formation of most interstellar molecules. The chemistry of H 3 + in dense (molecul...

Deuterium Fra tionation in Interstellar Clouds

Exotic clouds in the local interstellar medium

The neutral interstellar medium (ISM) inside the Local Bubble (LB) has been known to have properties typical of the warm neutral medium (WNM). However, several recent neutral hydrogen (HI) absorption experiments show evidence for the existence of at least several cold diffuse clouds inside or at the boundary of the LB, with properties highly unusual relative to the traditional cold neutral medi...

On water ice formation in interstellar clouds

A model is proposed for the formation of water ice mantles on grains in interstellar clouds. This occurs by direct accretion of monomers from the gas, be they formed by gas or surface reactions. The formation of the first monolayer requires a minimum extinction of interstellar radiation, sufficient to lower the grain temperature to the point where thermal evaporation of monomers is just offset ...