Supersonic nozzles

Sinha M P, Schulz A and Zare R N 1973 Internal state distribution of alkali dimers in supersonic nozzle beams J. Chem. Phys. 58 549-56... 

In a solid-propellant rocket motor, the propellant is contained within the wall of the combustion chamber, as shown in Fig. 1. This contrasts with liquid systems, where both the fuel and oxidizing components are stored in tanks external to the combustion chamber and are pumped or pressure-fed to the combustor. In hybrid systems, one component, usually the fuel, is contained in the combustion chamber, while the other component is fed to the chamber from a separate storage tank, as in liquid systems. The solid-propellant motor also has an ignition system located at one end to initiate operation of the rocket. The supersonic nozzle affects the conversion of... 

Recently, a revival of electron ionisation LC-MS has been proposed by development of LC-SMB-MS [529]. In this system, the LC output (50-250 p,Lmin 1) is vaporised at atmospheric pressure and expanded from a supersonic nozzle into the vacuum system... 

Of course, commercially available transition metal complexes are stable at room temperature because they have achieved an 18-electron noble gas-like electronic configuration. Thus, molecules like iron pentacarbonyl [Fe(CO)s], ferrocene [Fe(C5H5)2], as well as piano-stool complexes such as C5H5Co(CO)2 are chemically quite inert. In order to study bimolecular reactions, it is necessary to first prepare unsaturated complexes. For studies using molecular beams, one approach is through photolysis of a stable volatile precursor in a supersonic nozzle. 

Corion Technologies, Supersonic nozzle electrostatic neutralizer, Corion Technologies, Inc., product literature, Woburn, MA (1989)... 

A technique which is not a laser method but which is most useful when combined with laser spectroscopy (LA/LIF) is that of supersonic molecular beams (27). If a molecule can be coaxed into the gas phase, it can be expanded through a supersonic nozzle at fairly high flux into a supersonic beam. The apparatus for this is fairly simple, in molecular beam terms. The result of the supersonic expansion is to cool the molecules rotationally to a few degrees Kelvin and vibrationally to a few tens of degrees, eliminating almost all thermal population of vibrational and rotational states and enormously simplifying the LA/LIF spectra that are observed. It is then possible, even for complex molecules, to make reliable vibronic assignments and infer structural parameters of the unperturbed molecule therefrom. Molecules as complex as metal phthalocyanines have been examined by this technique. 

Supersonic Nozzle Beams (Anderson, Andres, Feim)... 

Fig. 8.12 Schematic cross section of a supersonic nozzle isotope separator of radial design (Modified from Becker, E. W. Uranium Enrichment, Villani, S.,...

The FJ test is similar to an aerodynamic wind-turmel test used for supersonic aircraft, except for the airflow condition. A ducted rocket projectile is mounted on a thrust stand and the projectile and thmst stand are placed in a test chamber. A supersonic airflow simulating the flight conditions is suppHed to the projectile through a supersonic nozzle attached to the front-end of the test chamber. The pressure and temperature in the test chamber are kept equivalent to the flight alHtude conditions. The aerodynamic drag on the projectile and the thmst generated by the ducted rocket are measured directly by the FJ test. The airflow surrounding the projectile and the combustion gas expelled from the ramburner flow out from the exhaust pipe attached to the rear-end of the test chamber. 

At or near sonic velocity, as at the C-J plane and beyond, a minute divergence had a marked effect. Similarly, at the throat of supersonic nozzle, an infinitesimal change in cross-sectional area produced a finite acceleration of the flow. Objection was raised, however, by Duff Knight (Ref 17a) that evidence of a large density gradient at the end of the reaction zone is lacking. Wood Kirkwood (Ref 17b) suggested that even in normal detonation, the reactions are incomplete at the C-J point in a tube of finite diameter (Ref 22, p lid)... 

One issue that is particularly interesting for activated dissociation is the importance of translational vs. vibrational activation since this relates to the topology of the barrier location on the PES (see Section 2.3.1). In analyzing experiments, it has been traditional to define the vibrational efficacy rjv as in eq. (2.5). This analysis, however, assumes that A(v) is the same for all v and this may not be universally true. In this case, describing vibrational efficacy is more complicated. Very recently, experiments for CH4 dissociation on transition metals even combine supersonic nozzle molecular beams with laser state preparation techniques to probe the reactivity of specifically prepared vibration rotation states [115-118] (see Section 4.3.1.3). 

Gas-surface dynamics experiments using initial state preparation techniques are still relatively uncommon. Molecules with permanent dipole moments can be oriented in hexapole electric fields. For example, NO from a supersonic nozzle can be fully quantum state selected in such fields and this allows studies of the dependence of S or scattering P on molecular orientation to the surface, i.e., N end down or end down [128]. Some of these experiments are described in Section 4.2. 

Beams, Supersonic Nozzle (Anderson, Andres, Fenn). 10 275... 

In 1984. scientists (Rohlling. Cox. and Caldor at Exxon Research and Engineering) created clusters of carbon (soot) by the laser vaporization of a carbon target rod in connection with a supersonic nozzle. By means of mass spectroscopy, the researchers determined the relative abundance of the carbon clusters produced. Small, 20- to 40-atom clusters of carbon were expected inasmuch as these had been produced a number of times by earlier investigators working on the soot problem. In such experiments, an interesting but unexplained question always arose—Why were only even-numbered carbon clusters produced in the complete absence of odd-numbered clusters See Fig. 3. 

Scattering studies with metastable atoms are in many cases easier (and less expensive) than experiments with ground-state atoms, The discussion that follows is mainly concerned with helium, as most of the information is available for this atom. Figure 2 shows a skeletal setup of the experiment. A helium beam from a supersonic nozzle source is excited by electron impact to its two metastable states. The singlet state can be quenched by the 2g radiation from a helium-gas discharge lamp ... 

Notations 1 - swirling device, 2 - sub/ supersonic nozzle, 3 - working section, 4 -device for gas-liquid mixture withdrawal, 5 - diffuser... 

Sinha, M.P., Caldwell, C.D. and Zare, R.N. (1974). Alignment of molecules in gaseous transport Alkali dimers in supersonic nozzle beams, J. Chem. Phys., 61, 491-503. 

Westenberg, A., Favin, R.M., Complex Kinetics in Supersonic Nozzle Flow, Ninth Symp. Int. on Combustion, Academic Press, New York, 1963, pages 785-798. 

A static fill, an effusive beam or a supersonic nozzle can be used for the introduction of the gas sample,. The supersonic nozzle has the advantage of refrigeration, and one may study rotationally and vibrationally cold molecules, or even stabilize otherwise inaccessible van der waals molecules. Finally, when operated in a pulsed mode, the nozzle cycle can be matched to the duty cycle of the laser to optimize the measuring conditions and improve the background vacuum. 

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