Buffer gas pressure

The basie flow system is eoneeptiially straightforward. A earrier gas, often helium, flows into the upstream end of a tube approximately 1 m long with a radius of several eentimetres. This buffer gas pressure is approximately 100 Pa. Ions are ereated either in the flow tube or injeeted from an external soiiree at the... 

Parameter studies have shown that single-layer nanotubes can be produced by the arc method under a wide range of conditions, with large variations in variables such as the buffer gas pressure (100-500 Torr), gas flow rate, and metal concentration in the... 

Are the buffer gas pressure and the partial pressure of the reactant neutral significantly lower in portions of the sampled volume than in the bulk of the ion source ... 

Plots of dephasing rate versus buffer gas pressure allow us to extract homogeneous dephasing cross sections according to equation (2). In Fig. 3 (bottom) we show Iodine coherence dephasing data for propane buffer gas. Note the similarity of the extracted cross sections in both the PE and RTG cases. These measurements were repeated for a series of buffer gases and the results are contained in Table l.[3]... 

Rate constants have been measured for the reaction of CI with CH3B1- over buffer gas pressures from 300-1100 Torr at 125 °C by ion mobility spectrometry (IMS).72 The experiments indicate that this reaction is not moved onto its high-pressure limit of kinetic behaviour by the use of buffer gas pressures near 1 atm. The same authors have carried out a similar study of the reaction of CI with isopropyl bromide at 640 Torr and 20-175 °C.73 It was concluded that under these conditions the reaction occurs primarily by a distinctly two-step mechanism ... 

Kratschmer et al. (1990) vaporized graphite in the presence of He buffer gas, examined the soot collected and observed that the intensity of the uv and infrared absorption features characteristic of C60 were buffer gas pressure dependent. At a pressure of about 1.3 x 103 Pa (10 Torr), these features are absent, but are clearly... 

Clustering at very high temperatures, as with high buffer gas pressures in graphite vaporization, is unfavourable to C60 formation because Cf0F itself becomes more reactive under such conditions. If the temperature decreases too rapidly, as with low... 

In Table I, the bimolecular rate constants for C2 X3Eg and a3II which we measured are tabulated. The experiments were carried out over a wide range of laser powers, buffer gas pressures, and precursor molecule pressures to assure that the experimental data does not contain artifacts due to three body reactions, vibrational quenching, fragment diffusion, or other fragment reaction. 

When the heat-pipe Is In a steady state the pressure of the metal vapor Is equal to that" of the buffer gas. The vapor pressure In the Isothermal zone Is thus determined by measuring the buffer gas pressure with an MKS Baratron capacitance manometer. 

In his careful, high resolution studies of the HPS lamp, Whittaker (1 3) observed most of the expected atomic lines of Na, e.g., from the principal, sharp, diffuse and fundamental series as classically designated. Also observed were forbidden lines of the Lenard series from P and -> P transitions. Two forbidden lines at 552.7 and 553.2 nm are prominent on the "knee" of the blue wing reversal of the resonance lines. Many of these atomic lines are also broadened at higher lamp reservoir temperatures and buffer gas pressures. In addition atomic lines of Hg and impurity lines of A1, Ba, Ca, K, Mg and Sr were observed. 

The detailed kinetics and energetics of the reactions in the rf-ion trap can be understood by considering that the total pressure inside the ion trap is on the order of 1 Pa, which means that the experiment is operating in the kinetic low-pressure regime. Therefore, a Lindemann-t3rpe mechanism has to be considered for each reaction step, and the reaction rates depend on the buffer gas pressure [187, 188]. As a consequence, the obtained pseudo first order rate constant k contains the termolecular rate constant as well as the concentrations of the helium buffer gas and of the reactants in the case of the adsorption reaction of the first CO molecule (1.1) ... 

Fig. 4.7. The spectrum of Sr, showing high Rydberg members and the emergence of supernumerary series members (denoted by arrows), due to the influence of collisions. Note their dependence on buffer gas pressure (after M. Nawaz et al. [148]).

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