Laser chemistry of organometallics as a general synthetic route to metal clusters

Chaiken, J.; Casey, M. J.; Villarica, M.

doi:10.1021/j100187a001

Cited by 22 publications

(16 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The lognormal distribution model has been successfully applied for fitting data on cluster size in both experiments [31][32][33] and Monte Carlo simulations 34 of the cluster aggregation process. The experimental and simulation conditions were spatially uniform.…”

Section: Cluster Size Distributionsmentioning

confidence: 99%

Combined molecular dynamics–direct simulation Monte Carlo computational study of laser ablation plume evolution

Zeifman

Garrison

Zhigilei

2002

Journal of Applied Physics

View full text Add to dashboard Cite

A two-stage computational model of evolution of a plume generated by laser ablation of an organic solid is proposed and developed. The first stage of the laser ablation, which involves laser coupling to the target and ejection of molecules and clusters, is described by the molecular dynamics (MD) method. The second stage of a long-term expansion of the ejected plume is modeled by the direct simulation Monte Carlo (DSMC) method. The presence of clusters, which comprise a major part of the overall plume at laser fluences above the ablation threshold, presents the main computational challenge in the development of the combined model. An extremely low proportion of large-sized clusters hinders both the statistical estimation of their characteristics from the results of the MD model and the following representation of each cluster size as a separate species, as required in the conventional DSMC. A number of analytical models are proposed and verified for the statistical distributions of translational and internal energies of monomers and clusters as well as for the distribution of the cluster sizes, required for the information transfer from the MD to the DSMC parts of the model. The developed model is applied to simulate the expansion of the ablation plume ejected in the stress-confinement irradiation regime. The presence of the directly ejected clusters drastically changes the evolution of the plume as compared to the desorption regime. A one-dimensional self-similar flow in the direction normal to the ablated surface is developed within the entire plume at the MD stage. A self-similar two-dimensional flow of monomers forms in the major part of the plume by about 40 ns, while its counterpart for large clusters forms much later, leading to the plume sharpening effect. The expansion of the entire plume becomes self-similar by about 500 ns, when interparticle interactions vanish. The velocity distribution of particles cannot be characterized by a single translational temperature; rather, it is characterized by a spatially and direction dependent statistical scatter about the flow velocity. The cluster size dependence of the internal temperature is mainly defined by the size dependence of the unimolecular dissociation energy of a cluster.

show abstract

Section: Cluster Size Distributionsmentioning

confidence: 99%

Combined molecular dynamics–direct simulation Monte Carlo computational study of laser ablation plume evolution

Zeifman

Garrison

Zhigilei

2002

Journal of Applied Physics

View full text Add to dashboard Cite

show abstract

“…Neglecting dissociation is a good approximation in the early stages of agglomeration, when n k decreases rapidly with k . By replacing the general equations by his phenomenological equations (for constant volume and temperature), Smoluchowski opened the way to analytic solutions for a variety of problems .…”

Section: Introductionmentioning

confidence: 99%

“…Assuming that the K ij must be proportional to collision rate constants and that collision rate constants are proportional to ( i α + j α ) μ ( i β + j β ) − ν , we and others suggested that the K ij could be approximated as C ( k > ) μ ( k < ) − ν , where k > is the greater of i and j . However, it is easy to show that the approximation of ( i α + j α ) μ ( i β + j β ) − ν by ( k > ) μ ( k < ) − ν is very poor unless i and j are very different.…”

Section: Introductionmentioning

confidence: 99%

Rate Constants and Sticking Coefficients for H₂ and He Obtained by Analysis of Agglomeration in a Nozzle Beam

Goodisman

Chaiken

2016

Int J of Chemical Kinetics

View full text Add to dashboard Cite

Cluster-cluster reaction rate constants are obtained from measurements of coalescence in nozzle-beam expansions. Coalescence is described by the Smoluchowski equations, modified to accommodate changes in volume and temperature. The asymptotic form of the cluster size distribution can reveal the scaling of the second-order rate constants K jk with the sizes of colliding particles. Scalings derived in the past are demonstrably incorrect and physically unjustifiable. Here, we use the physically reasonable scaling, K jk = K 11 j μ k μ , to study H 2 coalescence in a nozzle beam. Experimental size distributions fit the predicted asymptotic form, N k = Ak a e −bk , very well, with deviations identifying magic numbers. We obtain the base agglomeration cross section K 11 and the parameter μ, and thus all the rate constants, for H 2 . By comparing with products of geometric cross section and relative velocity, we find sticking coefficients. Experimental results for a nozzle-beam expansion of He are analyzed similarly, to yield K 11 and μ, and hence sticking coefficients, for He. These are compared to those for H 2 .

show abstract

“…The principal objectives of this study were to determine if it initiates according to the homogeneous initiation model and develop a Popplot for the material. This model was originally developed by Chaiken [1] and Campbell, Davis and Travis [2] and later modified to include a measurable reactive wave buildup by Sheffield, Engelke, and Alcon [3]. FEFO has a quite different chemical makeup than nitromethane (NM), making it more energetic, less sensitive, etc., and offering an important test case for the model.…”

Section: Introductionmentioning

confidence: 99%

Shock initiation and detonation properties of bisfluorodinitroethyl formal (FEFO)

Gibson¹,

Sheffield²,

Dattelbaum³

et al. 2012

AIP Conference Proceedings

View full text Add to dashboard Cite

Abstract. FEFO is a liquid explosive with a density of 1.60 g/cm 3 and an energy output similar to that of trinitrotoluene (TNT), making it one of the more energetic liquid explosives. Here we describe shock initiation experiments that were conducted using a two-stage gas gun using magnetic gauges to measure the wave profiles during a shock-to-detonation transition. Unreacted Hugoniot data, time-to detonation (overtake) measurements, and reactive wave profiles were obtained from each experiment. FEFO was found to initiate by the homogeneous initiation model, similar to all other liquid explosives we have studied (nitromethane, isopropyl nitrate, hydrogen peroxide). The new unreacted Hugoniot points agree well with other published data. A universal liquid Hugoniot estimation slightly under predicts the measured Hugoniot data. FEFO is very insensitive, with about the same shock sensitivity as the triamino-trinitro-benzene (TATB)-based explosive PBX9502 and cast TNT.

show abstract

Laser chemistry of organometallics as a general synthetic route to metal clusters

Cited by 22 publications

References 0 publications

Combined molecular dynamics–direct simulation Monte Carlo computational study of laser ablation plume evolution

Combined molecular dynamics–direct simulation Monte Carlo computational study of laser ablation plume evolution

Rate Constants and Sticking Coefficients for H₂ and He Obtained by Analysis of Agglomeration in a Nozzle Beam

Shock initiation and detonation properties of bisfluorodinitroethyl formal (FEFO)

Contact Info

Product

Resources

About

Laser chemistry of organometallics as a general synthetic route to metal clusters

Cited by 22 publications

References 0 publications

Combined molecular dynamics–direct simulation Monte Carlo computational study of laser ablation plume evolution

Combined molecular dynamics–direct simulation Monte Carlo computational study of laser ablation plume evolution

Rate Constants and Sticking Coefficients for H2 and He Obtained by Analysis of Agglomeration in a Nozzle Beam

Shock initiation and detonation properties of bisfluorodinitroethyl formal (FEFO)

Contact Info

Product

Resources

About

Rate Constants and Sticking Coefficients for H₂ and He Obtained by Analysis of Agglomeration in a Nozzle Beam