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The dynamics of the C+NO→CN+O and C+N2O→CN+NO reactions are reinvestigated using a pulsed supersonic crossed molecular beam apparatus. Laser vaporization of graphite at the exit of a pulsed nozzle is used to produce the atomic carbon beam. Laser induced fluorescence spectra of the CN scattered product have been obtained for both reactions. [ABSTRACT FROM AUTHOR]

Molecular scattering at collisional energies of the order of 10-100  cm-1 (corresponding to kinetic temperatures in the 15-150 K range) provides insight into the details of the scattering process and, in particular, of the various resonances that appear in inelastic cross sections. In this Letter, we present a detailed experimental and theoretical study of the rotationally inelastic scattering of ground-state ortho-D2O by ground-state para-H2 in the threshold region of the D2O(000→202) transition at 35.9  cm-1. The measurements were performed with a molecular crossed beam apparatus with variable collision angle, thence with variable collisional energy. Calculations were carried out with the coupled-channel method combined with a dedicated high-level D2O-H2 intermolecular potential. Our theoretical cross section 000→202 is found to display several resonance peaks in perfect agreement with the experimental work, in their absolute positions and relative intensities. We show that those peaks are mostly due to shape resonances, characterized here for the first time for a polyatomic molecule colliding with a diatom. [ABSTRACT FROM AUTHOR]

The reaction between atomic carbon and acetylene has been investigated using complementary crossed molecular beam techniques. Differential cross sections have been obtained for the reactions of both ground and excited carbon atoms, C(³P[sub J], ¹D[sub 2])+ C[sub 2]H[sub 2](X ¹Σ[sup +, sub g], in experiments conducted with continuous supersonic beams, mass spectrometric detection, and time-of-flight analysis at a relative translational energy of 29.3 kJmol[sup -1]. The reaction C(³P[sub J]) + C[sub 2]H[sub 2](X ¹Σ[sup +, sub g]) has been found to lead to C[sub 3]H+H and C[sub 3]+H[sub 2] products in comparable amounts. Both H and H[sub 2] elimination pathways are found to proceed through the formation of a C[sub 3]H[sub 2] long-lived intermediate complex whose lifetime may be comparable to its rotational period. The spin-forbidden H[sub 2] elimination channel is attributed to the occurrence of intersystem-crossing between the triplet and singlet manifolds of the C[sub 3]H[sub 2] potential-energy surfaces. The reaction C(¹D[sub 2])+C[sub 2]H[sub 2](X ¹Σ[sup +, sub g]) has been found to lead to formation of C[sub 3]H+H, with a C[sub 3]H center-of-mass angular distribution strongly forward peaked, indicating a short-lived intermediate complex. Integral cross sections have been obtained for the C(³P[sub J]j) + C[sub 2]H[sub 2] (X &sup1Σ[sup +, sub g]) → C[sub 3] H + H(²S[sub ½]) reaction in experiments conducted with pulsed, supersonic molecular beams in the range of relative translational energies E[sub T]=0.38 -25.5 kJ mol[sup -1], the H(²S[sub ½) product being detected by laser-induced fluorescence. The reaction has been found to be without a barrier, relative integral cross sections being proportional to (Er)[sup -0.80&plumsn;0.03] below E[sub T]=10 kJmol[sup -1]. These findings provide direct evidence that the C(³P[sub J]) +C[sub 2]H[sub 2] reaction can occur under... [ABSTRACT FROM AUTHOR]

Background: Evacuation of gastric content through a nasogastric tube, followed by rapid sequence induction, is usually recommended in infants undergoing pyloromyotomy. However, rapid sequence induction may be challenging, and is therefore controversial. Some anaesthetists regularly perform classical non-rapid induction technique, after blind aspiration of the gastric contents, although this aspiration may have been incomplete. This prospective observational study aimed to assess whether the ultrasound monitoring of the aspiration of the stomach contents, may be useful to appropriately guide the choice of the anaesthetic induction technique, in infants undergoing pyloromyotomy.Methods: Infants undergoing pyloromyotomy were consecutively included. Ultrasound assessment of the antrum was performed before and after the aspiration of the gastric contents through a 10 French gastric tube. The stomach was defined as empty when no content was seen in both supine and right lateral positions. The correlation between antral area and the aspirated gastric volume was also tested.Results: We analysed 34 infants. Ultrasound examination of the antrum failed in three infants. The stomach was empty in 30/34 infants (nine before aspiration, 21 after aspiration), allowing to perform a non-rapid induction technique in 88.2% of the infants. There was a significant correlation between antral area measured in right lateral decubitus and the aspirated gastric volume.Conclusions: Our results suggest that the qualitative ultrasound assessment of the antral content may be a simple and useful point-of-care tool, for the choice of the most appropriate anaesthetic technique for pyloromyotomy according to the estimated risk of pulmonary aspiration of gastric contents. [ABSTRACT FROM AUTHOR]

Context. Oxygen molecules (O2) are of particular interest because of their crucial role in astrochemisty. Modelling of O2 molecular emission spectra from interstellar clouds requires the calculation of rate coefficients for excitation by collisions with the most abundant species. Aims. Rotational excitation of O2(X3Σ -) by H2 is investigated theoretically and experimentally and we check the validity of the local thermodynamic equilibrium (LTE) approach for interpreting O2 observations. Methods. Using a new ab initio potential energy surface, collisional excitation of O2 is studied using a full close-coupling approach. The theoretical calculations are validated by comparison with crossed beam scattering experiments. We also performed calculations for the excitation of O2 from a large velocity gradient (LVG) radiative transfer code using the new rate coefficients. Results. State-to-state rate coefficients between the 27 lowest levels of O2 were calculated for temperatures ranging from 5 K to 150 K. The critical densities of the O2 lines are found to be at ≳104 cm-3 for temperatures higher than 50 K. This value is slightly larger than the one previously determined using previous He rate coefficients. Conclusions. The new rate coefficients will help in interpreting O2 emission lines observed where LTE conditions are not fully fulfilled and enable an accurate determination of the O2 abundance in the interstellar medium. [ABSTRACT FROM AUTHOR]