Deuterium fractionation on interstellar grains studied with modified rate equations and a Monte Carlo approach

Caselli, P.; Stantcheva, Tatiana; Shalabiea, Osama M.; Shematovich, V. I.; Herbst, Eric

doi:10.1016/s0032-0633(02)00092-2

Cited by 91 publications

(140 citation statements)

References 24 publications

Supporting

Mentioning

135

Contrasting

Order By: Relevance

“…If we assume now that water ices are formed at the same time by hydrogenation of oxygen atoms sticking on the grain surfaces, the deuteration degree is set by the atomic D/H ratio of the accreting gas (e.g. Tielens 1983;Caselli et al 2002), and cannot be substantially different in the three species (water, formaldehyde and methanol), unless selective deuteration is at work in formaldehyde and methanol with respect to water. Detailed chemical models have been developed for the deuterium fractionation on grain surfaces.…”

Section: Discussionmentioning

confidence: 99%

Search for solid HDO in low-mass protostars

Parise

Simon

Caux

et al. 2003

A&A

View full text Add to dashboard Cite

Abstract. We present ground-based 2.1 to 4.2 µm observations of four low-mass protostars. We searched for the 4.1 µm OD stretch band, characteristic of solid HDO in grain mantles. We did not detect solid HDO in any of the four sources, but we derive 3σ upper limits from 0.5% to 2% for the HDO/H 2 O ratio depending on the source. These ratios provide strong constraints to solid-state deuteration models when compared to deuterium fractionation values observed in the gas phase. We discuss various scenarios that could lead to such a low water deuteration compared to the high formaldehyde and methanol deuteration observed in the gas-phase.

show abstract

Section: Discussionmentioning

confidence: 99%

Search for solid HDO in low-mass protostars

Parise

Simon

Caux

et al. 2003

A&A

View full text Add to dashboard Cite

show abstract

“…For CO + O → CO 2 we took 1000 K (d 'Hendecourt et al 1985). The surface rates were altered according to Stantcheva et al (2001) and Caselli et al (2002) in order to cope with the discrete aspects of grain surface chemistry. This so called "modified rate approach" has been tested against a more detailed stochastic method by Stantcheva & Herbst (2004) and shows reasonable agreement with it.…”

Section: Grain Surface Chemistrymentioning

confidence: 99%

Modeling the chemical evolution of a collapsing prestellar core in two spatial dimensions

Weeren¹,

Brinch

Hogerheijde³

2009

A&A

View full text Add to dashboard Cite

Context. The physical conditions in a collapsing cloud can be traced by observations of molecular lines. To correctly interpret these observations the abundance distributions of the observed species need to be derived. The chemistry in a collapsing molecular cloud is not in a steady state as the density and temperature evolve. We therefore need to follow chemical reactions, both in the gas phase and on dust grains, as well as gas-grain interactions, to predict the abundance distributions. Aims. Our aim is to model the abundances of molecules, in the gas phase and on grain mantles in the form of ice, from prestellar core collapse to disk formation. We want to investigate the need for grain surface reactions and compare our results with observed abundances, column densities, and ice-mantle compositions. Methods. We use a 2-dimensional hydrodynamical simulation as a physical model from which we take the density, temperature, and the flow of the gas. Trace particles, moving along with the gas, are used to follow the chemistry during prestellar core collapse and disk formation. We calculated abundance profiles and column densities for various species. The evolution of these abundances and the composition of ices on grain mantles were compared to observations and we tested the influence of grain surface reactions on the abundances of species. We also investigated the initial abundances to be adopted in more detailed modeling of protoplanetary disks by following the chemical evolution of trace particles accreting onto the disk. Results. Fractional abundances of HCO + , N 2 H + , H 2 CO, HC 3 N, and CH 3 OH from our model with grain surface reactions provide a good match to observations, while abundances of CO, CS, SO, HCN, and HNC show better agreement without grain surface reactions. The observed mantle composition of dust grains is best reproduced when we include surface reactions. The initial chemical abundances to be used for detailed modeling of a protoplanetary disk are found to be different from those in dark interstellar clouds. Ices with a binding energy lower than about 1200 K sublimate before accreting onto the disk, while those with a higher binding energy do not.

show abstract

“…If the deuteration of the three ices (H 2 S, H 2 CO, and CH 3 OH) occurs when the ices are formed, and if it is dominated by pure statistics (i.e., by the random distribution of D atoms), the deuteration ratios would assume the following values (detailed discussion is in Rodgers & Charnley 2002) Caselli et al (2002) to explain deuteration fractionation on interstellar grains indeed confirm the above values-assuming that the chemistry of S is similar to that of O on the grain surfaces.…”

Section: ϫ15mentioning

confidence: 99%

“…The diagonal line in Figure 2 shows the predicted D 2 S/HDS as a function of the atomic D/H ratio in the accreting gas, assuming that D 2 S/HDS is equal to D 2 O/HDO, as computed by Caselli et al (2002). The argument that the surface chemistries of sulfur and oxygen are similar can be challenged by the fact that D 2 O has not yet been detected in the ISM.…”

mentioning

confidence: 99%

First Detection of Doubly Deuterated Hydrogen Sulfide

Vastel

Phillips

Ceccarelli

et al. 2003

ApJ

107

View full text Add to dashboard Cite

This work was carried out using the Caltech Submillimeter Observatory and presents the observational study of HDS and D 2 S toward a sample of Class 0 sources and dense cores. We report the first detection of doubly deuterated hydrogen sulfide (D 2 S) in two dense cores and analyze the chemistry of these molecules, aiming to help understand the deuteration processes in the interstellar medium. The observed values of the D 2 S/HDS ratio and upper limits require an atomic D/H ratio in the accreting gas of 0.1-1. The study presented in this Letter supports the hypothesis that formaldehyde, methanol, and hydrogen sulfide are formed on the grain surfaces, during the cold prestellar core phase, where the CO-depleted gas has large atomic D/H ratios. The high values for the D/H ratios are consistent with the predictions of a recent gas-phase chemical model that includes and ϩ H 3 its deuterated isotopomers, H

show abstract

Deuterium fractionation on interstellar grains studied with modified rate equations and a Monte Carlo approach

Cited by 91 publications

References 24 publications

Search for solid HDO in low-mass protostars

Search for solid HDO in low-mass protostars

Modeling the chemical evolution of a collapsing prestellar core in two spatial dimensions

First Detection of Doubly Deuterated Hydrogen Sulfide

Contact Info

Product

Resources

About