Doppler regime

Figure C3.3.7. In the upper half of the figure are shown typical measured Doppler profiles for molecules scattered into the (OO O J= 72) or (OO l J = 17) states of CO2 by collisions with hot pyrazine having an energy of 40 640 cm In the lower half of the figure is shown a typical intennolecular potential identifying the hard and soft collision regimes and the kind of energy transfer they effect.

Nonintrusive Instrumentation. Essential to quantitatively enlarging fundamental descriptions of flow patterns and flow regimes are localized nonintmsive measurements. Early investigators used time-averaged pressure traverses for holdups, and pilot tubes for velocity measurements. In the 1990s investigators use laser-Doppler and hot film anemometers, conductivity probes, and optical fibers to capture time-averaged turbulent fluctuations (39). 

Beam Spectroscopy. Both specificity and sensitivity can be gready enhanced by suppressing coUisional and Doppler broadening. This is accompHshed in supersonic atomic and molecular beams (296) by probing the beam transversely to its direction of dow in a near-coUisionless regime. 

The calibration procedure is sufficiently accurate for Doppler velocities in the regime 0 to 10 mm s beyond this range, laser calibration is more suitable. Calibration with ot-iron, as described, can also be used for Mossbauer measurements with other isotopes, e.g., Ni, Au, and Ir, for which suitable standard absorbers are not available (provided that the Doppler velocity range of interest is not significantly greater than 10 mm s ). This, of course, requires that the spectrometer is temporarily equipped with a Co source and an a-iron absorber. 

So far, a modulator device has been described, not a filter. This can be used on a monochromatic (for example laser) input beam to vary the Doppler-shifted frequency or direction or intensity of an output beam as a function of input RF frequency and power. In order to understand how an AOTF device goes further than this, it is necessary to look at the effect of Bragg regime diffraction and the impact of the anisotropy of the AOTF crystal medium. 

The linewidth of annihilation from the free-positron state is Doppler-broadening measurements. In lifetime measurements the PsF component hides beneath the o-Ps component which has a similar lifetime. This is a case where the two-dimensional data analysis shows its great advantage As the Doppler broadening of each positron state is determined in its own time regime even positron states with similar features may be seperated from each other. Moreover, a tentative fitting procedure with only the three positron states as in pure water did not come to a satisfactory result with the AMOC histogram of the NaF solution. 

The burner of Case 1 uses a swirled injector (Fig. 9.1) where swirl is produced by tangential injection downstream of a plenum. A central hub contributes to flame stabilization. In the experiment methane is injected through holes located in the swirler but mixing is fast so that perfect premixing is assumed for computations. Experiments include LDV (Laser Doppler Velocimetry) measurements for the cold flow as well as a study of various combustion regimes. The dimensions of the combustion chamber are 86 mm X 86 mm x 110 mm. 

High resolution studies by conventional spectroscopy are genuinely hampered by Doppler-broadening of the rotation-vibration lines in the low pressure regime. Individual Doppler-shifted frequencies contribute to the (normalized) Doppler-broadened line shape, due to the distribution of molecular velocities along the direction of observation... 

The pedestal of the Doppler signal is obtained by applying a low-pass filter unit to the photodetector signal. As shown in Figure 7-3, the intensity of the scattered light depends in a characteristic way on particle size. From this relation three scattering regimes may be identified, where also the Mie-parameter, defined as a = JiDp(/l, is used to non-dimensionalize the particle... 

The PNF-coated shafts were assembled into the test chambers. The test chambers were flushed with isotonic saline to displace the air interface. The blood flow through each of the chambers was adjusted to 200 mL/min using a Ward s doppler flow ultrasound cuff. The rotation of the shafts was maintained at 200 rpm. Under these conditions, a laminar flow regime was maintained with a shear rate of 150 s-1. Experiments were carried out for time periods of 60 min. After completion of each of the experiments, the chamber was flushed with isotonic saline. 

Once the sample pressure has become sufficiently high that Doppler broadening may be neglected, the peak signal from an unsaturated spectral line becomes independent of the pressure for a particular sample composition (Section 1.2). In this regime Omax depends on frequency, temperature, linewidth and the molecular concentration of the state under study. As an isotopomer, stereoisomer or vibrational excimer, the species concentration will be less than that of its parent. 

The breakup parameter, Kbu, in the bag breakup and the stripping breakup regime is proportional to the characteristic breakup frequencies suggested by [5]. The characteristic breakup frequency for the catastrophic breakup regime is derived from the study of the RT instability by Bellman and Pennington [21] as reported by Patterson and Reitz [11]. The constant k = 0.05 has been determined such that the drop radii match the phase Doppler measurements of Schneider [22], whereas the values for the constants ki and k are chosen such that Kbu is continuous at the regime-dividing Weber numbers, Web,s and Wcg c-... 

FIGURE 11.2 Calculated Doppler speetrum of a dipole-forbidden transition of a single trapped ion oscillating at frequencies co/ln = 0.7 MHz and ajlii = 1 MHz and cooled down to the Lamb-Dicke regime sueh that the Lamb-Dieke parameters are 0.1 in both directions (the laser wavevector has the same projeetion along the coordinates axes and O ). (Figure courtesy of Caroline Champenois, PIIM, Marseille.)... 

Olmos E, Gentric C, Poncin S, Midoux N. (2003) Description of flow regime transitions in bubble columns via laser Doppler anemometry signals processing. Chem. Eng. Sci., 58 1731-1742. 

This result gives the modulation in a Doppler free form. The requirement is that the line be excited uniformly. The averaging over the velocity groups has introduced an additional Gaussian degradation term which can be rewritten in the form exp- (l/2) [ ( 2 -Q)/Q] (x/ ] is of no consequence in the regime in which we work since 2Xjj 2/(Q-Q ) is of order 400 nsec. For a pulse separation of x=400 nsec the echo which appears 2x =800 nsec or 50 fluorescence lifetimes later would suffer a diminished modulation amplitude of only e . It seems then that this technique can effectively utilize the abiltiy of the photon echo technique to observe excited atoms which live many times their natural lifetime. 

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