Transition cross section

Zone 2 is a transition zone, and its length depends upon the diffuser type. For a compact jet the transition zone typically extends to eight or ten diameters from the outlet. Within this zone, the maximum velocity may vary inversely with the square root of the distance from the outlet. Some researchers 3-5 suggest use of a simplified scheme of the jet (Fig. 7.20b) with a transition cross-section for practical purposes. 

Fig. 5.4. Rotational transition cross-section for Ar-N2 versus kinetic energy of collision (Kelvins) from [191]. (+) CC calculations of C2-.4 from [211].

Na is likely deposited in the upper atmosphere by meteors along with other metals (Clemesha et al., 1981) and distributed by solar winds (Happer et al., 1994). This atomic layer is "eaten away" at its bottom by chemical reactions (e.g. molecule and aggregate formation). Fe, Al, Ca are more abundant than Na, but the D2 transition is so strong that it provides the largest product of column density CNa and transition cross section, nominally 10 — 10" atoms/cm. The layer has been studied mostly with Lidar technique (Blamont and Donahue, 1961 Albano et al., 1970 Bowman et al., 1969 Sarrazin, 2001). 

In fact, the transition cross section can be written in terms of a line-shape function g(v) (with units of Hz ) in the following way ... 

The characteristics of the active medium determine those of the laser action. According to Equation (2.7), the gain G(v) is directly related with the particular characteristics of the quantum energy levels of the active medium via the transition cross section a. As follows from Sections 1.3 and 1.4 (see also Exercise 5.4) ... 

Cr + ions in aluminum oxide (the ruby laser) show a sharp emission (the so-called Ri emission line) at 694.3 nm. To a good approximation, the shape of this emission is Lorentzian, with Av = 330 GHz at room temperature, (a) Provided that the measured peak transition cross section is c = 2.5 x 10 ° cm and the refractive index is = 1.76, use the formula demonstrated in the previous exercise to estimate the radiative lifetime, (b) Since the measured room temperature fluorescence lifetime is 3 ms, determine the quantum efficiency for this laser material. 

As known from the basic quantum theory of transitions, cross-sections may be written as ... 

For the relatively narrow peak of energy losses with the maximum at ha)0n, the transition cross section a0n integrated over q and [Pg.315]

Op pump transition cross-section Q Rabi pulsation... 

Figure 5-71. A typical rapid-transit cross-section showing the elastomeric rail fasteners and floatings-slab supports. 

The experimental ESCA spectrum of PTFE< possesses four main peaks, three of intermediate intensity centered at approximately 20, 25, and 31 eV (peaks A, B, C, respectively), and one of high intensity at 41 eV (peak D). Since we have not included the contributions of the different atomic orbitals (transition probabilities) to the total transition cross-sections to establish the theoretical ESCA curves, we are not yet able to discuss the relative intensities of the peaks, but only their positions. 

Correlation, or many-body effects, can be classified according to the many-body factor Xx- If Xx is close to 1, the MO picture, the aufbau principle, a Koopmans theorem and the quasi-particle picture hold. The analysis of the Auger spectrum can then be conducted solely in terms of MO theory. When more than one Xx enters in the wavefunction, we have hole-mixing effects and electronic interference in the transition cross sections, in analogy to the case of photoelectron spectra. When only one Xx is large, but this Xx is present in more than one state, one can then not associate a one-to-one correspondence between MOs (or MO factors in Eq. 3.39) and spectral bands (states). The states in question are thus associated with a breakdown of the MO picture. It could, finally, also be that no Xx is large, in which case we talk about a correlation-state satellite. 

In terms of the radiative-transition cross section physical meaning of the condition for the rate of the stimulated (induced)... 

The rate of vibrational excitation of a molecule through multiple-photon absorption, Wexci depends on the radiation intensity I and the vibrational-transition cross sections ... 

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