Importance of Surface Morphology in Interstellar H
            <sub>2</sub>
            Formation

Hornekær, Liv; Baurichter, A.; Petrunin, V. V.; Field, D.; Luntz, A. C.

doi:10.1126/science.1090820

Cited by 162 publications

(175 citation statements)

References 14 publications

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“…The composition of the ice mantle depends primarily on the atomic composition of the gas phase, with a weaker dependence on grain temperature, through differences in the volatility of atomic species (Tielens & Hagen 1982). Recent simulations (Chang et al 2005) and lab experiments (Hornekaer et al 2003) show that the nature of the surface also plays an important role.…”

Section: Solid Phase Processesmentioning

confidence: 99%

The chemistry of high-mass star formation

Tak¹,

Floris²

2005

Proc. IAU

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Abstract. This paper reviews the chemistry of star-forming regions, with an emphasis on the formation of high-mass stars. We first outline the basic molecular processes in dense clouds, their implementation in chemical models, and techniques to measure molecular abundances. Then, recent observational, theoretical and laboratory developments are reviewed on the subjects of hot molecular cores, cosmic-ray ionization, depletion and deuteration, and oxygen chemistry. The paper concludes with a summary of outstanding problems and future opportunities.

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Section: Solid Phase Processesmentioning

confidence: 99%

The chemistry of high-mass star formation

Tak¹,

Floris²

2005

Proc. IAU

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“…2,[22][23][24][25][26] In high temperature H 2 /O 2 combustion, for example, collisions of the highly energized product H 2 O molecules with H 2 reactant provide an important mechanism for heat flow as well as establishing local thermodynamic equilibrium in the flames. 3 As a result, there is a broad set of energy dependent cross sections and temperature dependent kinetic rates for such processes at the stateto-state level that prove critical in achieving the desired optimal combustion efficiency.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, considerable effort has been put into characterizing H + H → H 2 reactions catalyzed by solid dust particles, [42][43][44] many of which are expected to be quite cold and coated by a water ice mantle. 25,33 As a result, this requires efficient recombination and desorption 45 of H 2 from the icy H 2 O surface, the detailed H 2 + H 2 O interaction potential for which is necessary to characterize these important interstellar rate processes.…”

Section: Introductionmentioning

confidence: 99%

Overtone vibrational spectroscopy in H2-H2O complexes: A combined high level theoretical ab initio, dynamical and experimental study

Ziemkiewicz

Pluetzer

Nesbitt

et al. 2012

The Journal of Chemical Physics

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First results are reported on overtone (v OH = 2 ← 0) spectroscopy of weakly bound H 2 -H 2 O complexes in a slit supersonic jet, based on a novel combination of (i) vibrationally mediated predissociation of H 2 -H 2 O, followed by (ii) UV photodissociation of the resulting H 2 O, and (iii) UV laser induced fluorescence on the nascent OH radical. In addition, intermolecular dynamical calculations are performed in full 5D on the recent ab initio intermolecular potential of Valiron et al. [J. Chem. Phys. 129, 134306 (2008)] in order to further elucidate the identity of the infrared transitions detected. Excellent agreement is achieved between experimental and theoretical spectral predictions for the most strongly bound van der Waals complex consisting of ortho (I = 1) H 2 and ortho (I = 1) H 2 O (oH 2 -oH 2 O). Specifically, two distinct bands are seen in the oH 2 -oH 2 O spectrum, corresponding to internal rotor states in the upper vibrational manifold of and rotational character. However, none of the three other possible nuclear spin modifications (pH 2 -oH 2 O, pH 2 -pH 2 O, or oH 2 -pH 2 O) are observed above current signal to noise level, which for the pH 2 complexes is argued to arise from displacement by oH 2 in the expansion mixture to preferentially form the more strongly bound species. Direct measurement of oH 2 -oH 2 O vibrational predissociation in the time domain reveals lifetimes of 15(2) ns and <5(2) ns for the and states, respectively. Theoretical calculations permit the results to be interpreted in terms of near resonant energy levels and intermolecular alignment of the H 2 and H 2 O wavefunctions, providing insight into predissociation dynamical pathways from these metastable levels.

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“…Molecular hydrogen formation on astrophysically relevant surfaces of silicates, carbon and ice has been studied by laboratory experiments during the past decade [45,46,47,48,49,50,51]. From the results of these experiments one can extract, for each surface, the energy barriers defined above and the density of adsorption sites.…”

Section: A Rate Equationsmentioning

confidence: 99%

Efficient stochastic simulations of complex reaction networks on surfaces

Barzel

Biham

2007

The Journal of Chemical Physics

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Surfaces serve as highly efficient catalysts for a vast variety of chemical reactions. Typically, such surface reactions involve billions of molecules which diffuse and react over macroscopic areas.Therefore, stochastic fluctuations are negligible and the reaction rates can be evaluated using rate equations, which are based on the mean-field approximation. However, in case that the surface is partitioned into a large number of disconnected microscopic domains, the number of reactants in each domain becomes small and it strongly fluctuates. This is, in fact, the situation in the interstellar medium, where some crucial reactions take place on the surfaces of microscopic dust grains. In this case rate equations fail and the simulation of surface reactions requires stochastic methods such as the master equation. However, in the case of complex reaction networks, the master equation becomes infeasible because the number of equations proliferates exponentially.To solve this problem, we introduce a stochastic method based on moment equations. In this method the number of equations is dramatically reduced to just one equation for each reactive species and one equation for each reaction. Moreover, the equations can be easily constructed using a diagrammatic approach. We demonstrate the method for a set of astrophysically relevant networks of increasing complexity. It is expected to be applicable in many other contexts in which problems that exhibit analogous structure appear, such as surface catalysis in nanoscale systems, aerosol chemistry in stratospheric clouds and genetic networks in cells.

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Importance of Surface Morphology in Interstellar H ₂ Formation

Cited by 162 publications

References 14 publications

The chemistry of high-mass star formation

The chemistry of high-mass star formation

Overtone vibrational spectroscopy in H2-H2O complexes: A combined high level theoretical ab initio, dynamical and experimental study

Efficient stochastic simulations of complex reaction networks on surfaces

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Importance of Surface Morphology in Interstellar H 2 Formation

Cited by 162 publications

References 14 publications

The chemistry of high-mass star formation

The chemistry of high-mass star formation

Overtone vibrational spectroscopy in H2-H2O complexes: A combined high level theoretical ab initio, dynamical and experimental study

Efficient stochastic simulations of complex reaction networks on surfaces

Contact Info

Product

Resources

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Importance of Surface Morphology in Interstellar H ₂ Formation