Gas Phase Reactive Collisions at Very Low Temperature: Recent Experimental Advances and Perspectives

Canosa, André; Goulay, Fabien; Sims, Ian; Rowe, B. R.

doi:10.1142/9781848162105_0002

Cited by 30 publications

(35 citation statements)

References 71 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The resulting picture of the process is the following: the behavior can be understood on the average in terms of a classical Langevin (capture) model where centrifugal barriers determine the amount of reactive flux which reaches the barrierless transition state; additionally, the structure of the van der Waals well provides temporal trapping at short distances, thus helping the system to find its way to reaction for high partial waves. Comparison with landmark experimental data obtained using the crossed molecular beam machine with variable beam intersectionangle [24] (Bordeaux) and the CRESU technique [22,23] (Rennes) shows a fairly good agreement. Accurate electronic calculations of the LR interactions were required in order to propertly describe collisions at such low kinetic energy.…”

Section: Discussionmentioning

confidence: 54%

“…Luckily, emerging experimental techniques like the Crossed Stark decelerators [21] promise to provide detailed information on cold bimolecular collisions. More related with our work, CRESU (Reaction Kinetics in Uniform Supersonic Flow) experiments implemented in Rennes [22,23], and crossed molecular beam experiments performed in Bordeaux [24,25], are exploring barrierless reactions between neutral species in conditions aproaching the cold regime [26]. In particular, rate constants and cross-sections have been recently obtained for the title reaction at temperatures and kinetic energies as low as ∼ 5K (1K∼ 8.3 × 10 −3 KJ mol −1 ) [27].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Reaching the cold regime: S(1D) + H2 and the role of long-range interactions in open shell reactive collisions

Lara

Dayou

Launay

2011

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Reactive cross-sections for the collision of open shell S( 1 D) atoms with ortho-and para-hydrogen, in the kinetic energy range 1−120 K, have been calculated using the hyperspherical quantum reactive scattering method developed by Launay et al. [Chem. Phys. Lett. 169, 473 (1990)]. Short-range interactions, described using the ab initio potential energy surface by Ho et al., were complemented with an accurate description of the longrange interactions, where the main electrostatic (∼ R −5 ) and dispersion (∼ R −6 ) contributions were considered. This allows the comparison with recent experimental measurements of rate constants and excitation functions for the title reaction at low temperatures [Berteloite et al., accepted in Phys. Rev. Lett., 2010]. The agreement is fairly good. The behavior in the considered energy range can be understood on the average in terms of a classical Langevin (capture) model, where the centrifugal barriers determine the amount of reactive flux which reaches the barrierless transition state. Additionally, the structure of the van der Waals well provides temporal trapping at short distances thus allowing the system to find its way to the reaction at some classically-forbidden energies. Interestingly, the cross-section for para-hydrogen shows clearly oscillating features associated to the opening of new partial waves and to shape resonances which may be amenable to experimental detection.

show abstract

Section: Discussionmentioning

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Reaching the cold regime: S(1D) + H2 and the role of long-range interactions in open shell reactive collisions

Lara

Dayou

Launay

2011

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…However, in the experiments carried out to determine the S( 1 D) removal rate coefficients at low temperatures, the para/ortho fraction is that corresponding at room temperature (≈1:3). The underlying hypothesis is that, during the expansion (and previous cooling) to produce the molecular jet used in the experiments, 43,52 there is no ortho/para interconversion. Therefore the formula to determine the rate coefficients under these conditions is…”

Section: A Quasi-classical Trajectory Calculationsmentioning

confidence: 99%

Rate coefficients from quantum and quasi-classical cumulative reaction probabilities for the S(1D) + H2 reaction

Jambrina

Lara

Menéndez

et al. 2012

The Journal of Chemical Physics

View full text Add to dashboard Cite

Cumulative reaction probabilities (CRPs) at various total angular momenta have been calculated for the barrierless reaction S( 1 D) + H 2 → SH + H at total energies up to 1.2 eV using three different theoretical approaches: time-independent quantum mechanics (QM), quasiclassical trajectories (QCT), and statistical quasiclassical trajectories ( The results show that the differences between these two PES are relatively minor and mostly related to the different topologies of the well. In addition, the agreement between the three theoretical methodologies is good, even for the highest total angular momenta and energies. In particular, the good accordance between the CRPs obtained with dynamical methods (QM and QCT) and the statistical model (SQCT) indicates that the reaction can be considered statistical in the whole range of energies in contrast with the findings for other prototypical barrierless reactions. In addition, total CRPs and rate coefficients in the range of 20-1000 K have been calculated using the QCT and SQCT methods and have been found somewhat smaller than the experimental total removal rates of S( 1 D).

show abstract

“…Our experimental approach is briefly summarized below to provide the reader with some experimental background (Sabbah et al 2010). The experiments were performed using a continuous flow CRESU apparatus (Canosa et al 2008;Dupeyrat et al 1985), adapted for condensable species such as PAHs (Goulay et al 2006). This chemical reactor is designed to generate dense uniform flows using a Laval nozzle, over a wide range of temperatures (60-470 K) and containing high (supersaturated) concentrations of PAH vapors.…”

Section: Combined Experimental/theoretical Approachmentioning

confidence: 99%

Insights into the condensation of PAHsin the envelope of IRC +10216

Biennier

Sabbah

Klippenstein

et al. 2011

EAS Publications Series

View full text Add to dashboard Cite

Abstract. The mechanisms of nucleation and growth of carbon dust particles in circumstellar envelopes of carbon-rich stars in the red giant and AGB phases of their evolution are poorly understood. It has been proposed that the transition of gas phase species to solid particles, is achieved by the formation of a critical nucleus composed of two PAHs held together by van der Waals forces. Some insights into the validity of the nucleation of PAH molecules in the envelope can be gained through the investigation of the thermodynamics of dimers, representing the first stage towards condensation. We have performed experiments to identify the temperature range over which small PAH clusters form in saturated uniform supersonic flows. The kinetics of the formation has also been investigated. The experimental data have been combined with theoretical calculations. We unambiguously demonstrate that the association of small PAHs such as pyrene (C16H10) is slower than the destruction of the dimer in warm and hot environments such as IRC +10216. Our findings challenge a formation model based on the physical stacking of small PAH units in circumstellar shells of carbon rich stars.

show abstract

Gas Phase Reactive Collisions at Very Low Temperature: Recent Experimental Advances and Perspectives

Cited by 30 publications

References 71 publications

Reaching the cold regime: S(1D) + H2 and the role of long-range interactions in open shell reactive collisions

Reaching the cold regime: S(1D) + H2 and the role of long-range interactions in open shell reactive collisions

Rate coefficients from quantum and quasi-classical cumulative reaction probabilities for the S(1D) + H2 reaction

Insights into the condensation of PAHsin the envelope of IRC +10216

Contact Info

Product

Resources

About