Resonance broadening transitions

When the quasistatic contribution to the absorption coefficient, as described by eq. (1), is incorporated in the LTE model (5.) a more realistic emission spectrum of the HPS discharge results (de Groot and Woerdman, to be published). This is already evident when the quasistatic absorption spectrum is compared with the extrapolated dispersive, resonantly broadened Na D absorption profile (see Figure 3). In the far red wing (X > 650 nm) the contribution of the A Sj, - X Zg transition is much larger than the dispersive contribution in a LTE model the same holds for the emission spectrum. In the far blue wing (X< 560 nm) the contribution of the Ilg - transition likewise dominates the dispersive contribution. 

The FWHMs of lines 1 and 2 of the A/ spectrum of Fig. 7.4 are 0.14 and 0.21 meV ( 1.1 and 1.7 cm ), respectively, compared to 0.06meV ( 0.5 cm-1) for the sharpest line of this spectrum. By comparison with the Ga and In spectra, the complete spectrum of indium in silicon, without any resonant broadening is shown in Fig. 7.5. In this spectrum, as in the Al spectrum, some of the highest-energy transitions are identified as unresolved doublets or shoulders. The lines of the Al and Ga spectra are superimposed on the 2-phonon spectrum of silicon and the In spectrum on the 3-phonon spectrum,... 

In the preceding chapters and in the present one, values of the FWHMs of the EM electronic transitions have been considered, either as intrinsic characteristics of the transitions or in connection with the broadening mechanisms which depend on concentration, compensation ratio, or inhomogeneous impurity distribution. In Chaps. 6 and 7, examples of resonant broadening with lattice phonons, which depend on the difference between the phonons and electronic frequencies, have also been given and they are not considered here. The broadening due to the inhomogeneous Stark effect has been discussed in... 

Photon echoes Resonant interaction with inhomogeneously broadened transition pulse duration less than dephasing time two pulses spaced by echo time r, with pulse areas of 7t/2 and 7t, respectively... 

Doppler-Broadened Transition. Narrow Resonances of Two-Photon Transitions Willioul Doppler Broadening.—Nonlinear Resonances on Coupled Doppler-Broadened Transitions. Narrow Nonlinear Resonances in Spectroscopy. Nonlinear Atomic Laser Spectroscopy. Nonlinear Molecular Laser Spectroscopy. - Nonlinear Narrow Resonances in Quantum Electronics. Narrow Nonlinear Resonances in Experimental Physics. 

To conduct FLN experiments, then, if a laser tuned to some portion of the absorption possessing a resolution comparable to the natural width of the isochromats is used to excite a finite subset of the constituents of the broadened transition, only those ions in resonance with the excitation will be capable of emitting luminescence. The resulting spectrum will differ from the emission observed through conventional broadband excitation, the luminescence is said to have been narrowed or FLN. This process is illustrated in fig. 4 where narrowing is demonstrated in the state of Pr in LaFj. 

Fig. 2.7 Excitation resonance broadening of a two-level system with increasing laser radiation intensity (w is the field frequency, ujo is the central transition frequency, F = jTi is the homogeneous spectral-line half-width, and G is the saturation parameter).

The fundamental advantage of the RF optical double-resonance technique is the high spectral resolution which is not limited by the optical Doppler width. Although the optical excitation may occur on a Doppler-broadened transition, the RF-optical double resonance signal IpiCt rf) is... 

According to the quantum transition state theory [108], and ignoring damping, at a temperature T h(S) /Inks — a/ i )To/2n, the wall motion will typically be classically activated. This temperature lies within the plateau in thermal conductivity [19]. This estimate will be lowered if damping, which becomes considerable also at these temperatures, is included in the treatment. Indeed, as shown later in this section, interaction with phonons results in the usual phenomena of frequency shift and level broadening in an internal resonance. Also, activated motion necessarily implies that the system is multilevel. While a complete characterization of all the states does not seem realistic at present, we can extract at least the spectrum of their important subset, namely, those that correspond to the vibrational excitations of the mosaic, whose spectraFspatial density will turn out to be sufficiently high to account for the existence of the boson peak. 

A unique situation is encountered if Fe-M6ssbauer spectroscopy is applied for the study of spin-state transitions in iron complexes. The half-life of the excited state of the Fe nucleus involved in the Mossbauer experiment is tj/2 = 0.977 X 10 s which is related to the decay constant k by tj/2 = ln2/fe. The lifetime t = l//c is therefore = 1.410 x 10 s which value is just at the centre of the range estimated for the spin-state lifetime Tl = I/Zclh- Thus both the situations discussed above are expected to appear under suitable conditions in the Mossbauer spectra. The quantity of importance is here the nuclear Larmor precession frequency co . If the spin-state lifetime Tl = 1/feLH is long relative to the nuclear precession time l/co , i.e. Tl > l/o) , individual and sharp resonance lines for the two spin states are observed. On the other hand, if the spin-state lifetime is short and thus < l/o) , averaged spectra with intermediate values of quadrupole splitting A q and isomer shift 5 are found. For the intermediate case where Tl 1/cl , broadened and asymmetric resonance lines are obtained. These may be the subject of a lineshape analysis that will eventually produce values of rate constants for the dynamic spin-state inter-conversion process. The rate constants extracted from the spectra will be necessarily of the order of 10 -10 s"F... 

It is much more difficult to observe the Mossbauer effect with the 130 keV transition than with the 99 keV transition because of the relatively high transition energy and the low transition probability of 130 keV transition, and thus the small cross section for resonance absorption. Therefore, most of the Mossbauer work with Pt, published so far, has been performed using the 99 keV transition. Unfortunately, its line width is about five times larger than that of the 130 keV transition, and hyperfine interactions in most cases are poorly resolved. However, isomer shifts in the order of one-tenth of the line width and magnetic dipole interaction, which manifests itself only in line broadening, may be extracted reliably from Pt (99 keV) spectra. 

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