Doppler line shape

Figure B2.5.12 shows the energy-level scheme of the fine structure and hyperfme structure levels of iodine. The corresponding absorption spectrum shows six sharp hyperfme structure transitions. The experimental resolution is sufficient to detennine the Doppler line shape associated with the velocity distribution of the I atoms produced in the reaction. In this way, one can detennine either the temperature in an oven—as shown in Figure B2.5.12 —or the primary translational energy distribution of I atoms produced in photolysis, equation B2.5.35.

Figure 9.26 (a) Doppler line shape with a Lamb dip. (b) As in (a) but with modulation and phase-... 

Zare, R.N. and Hershbach, D.R. (1963). Doppler line shape of atomic fluorescence excited by molecular photodissociation, Proc. IEEE 51, 173-182. 

An improved Doppler method has been used recently. In this method the probe laser is delayed relative to the dissociation laser so that only the products that fly parallel or antiparallel to the detection laser are excited. This yields much better state resolution and a deconvolution of complicated Doppler line shapes is no longer necessary. 

On the other hand, suppose Vq increases by AVq, then, in virtue of the dependence of w and tq on Vq, by expanding the Doppler line shape (Exp. (2) for = 0) in series with respect to AVq we obtain... 

The absorption line width is determined by the frequency range equal to double frequency difference between uj = 0 and wi corresponding to half maximum absorption. For the Doppler line shape... 

This kind of analysis has also been used for Doppler line shapes of H-atom products in allyl photochemistry. ... 

Fig. 3.6.1 Collision, Voigt, and Doppler line shapes. All three are shown with the same maximum amplitude, and with the same width at half maximum amplitude. The Voigt line shape is one of a continuum of profiles between Gaussian and Lorentzian, depending on the degree of collision broadening.

The actual line shape in a spectrum is a convolution of the natural Lorentzian shape with the Doppler shape. It must be calculated for a given case as there is no simple fomuila for it. It is quite typical in electronic... 

This result, when substituted into the expressions for C(t), yields expressions identieal to those given for the three eases treated above with one modifieation. The translational motion average need no longer be eonsidered in eaeh C(t) instead, the earlier expressions for C(t) must eaeh be multiplied by a faetor exp(- co2t2kT/(2me2)) that embodies the translationally averaged Doppler shift. The speetral line shape funetion I(co) ean then be obtained for eaeh C(t) by simply Fourier transforming ... 

Many recombination and spectroscopic studies have been carried out in decaying rare-gas plasmas. Invariably, the buffer gas was the parent gas of the ion under study. In addition to recording the emitted spectra, Frommhold and Biondi60 examined the line shapes of many afterglow lines in neon and in argon. The intent was to find spectroscopic evidence for Doppler broadening of the lines which would prove that... 

FIGURE 14-8 (a) Meaning of equivalent width, W (b) Doppler and Lorentzian line-shapes for equivalent half-widths (c) transmission curves for an absorption line for a weak and strong absorber, respectively (adapted from Lenoble, 1993). 

Multiplying this expression by n yields the Voigt function that occurs in the description of spectral-line shapes resulting from combined Doppler and pressure broadening. We elaborate on these phenomena in Section I of Chapter 2. 

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