Spectral Line Profiles

Rayleigh scattered light from dense transparent media with nonuniform density. If these nonuniformities are time-independent, there will be no frequency shift of the scattered light. If, however, time-dependent density fluctuations occur, as e. g. in fluids, due to thermal or mechanical processes, the frequency of the scattered light exhibits a spectrum characteristic of this time dependence. The type of information which can be obtained by determining the spectral line profile and frequency shift is described in an article by Mountain 235). 

The dipole autocorrelation function, C(t), is the Fourier transform of the spectral line profile, g(v). Knowledge of the correlation function is theoretically equivalent to knowledge of the spectral profile. Correlation functions offer some insight into the molecular dynamics of dense fluids. 

It is therefore a molecular parameter for the absorption strength when two photons are absorbed in the same quantum act by one molecule (Fig. 3.1a). 5 has the unit cm4-s-molecule photon The term yM(2m) stands for spectral line profile of the material. Furthermore, Eq. (6) describes the number of molecules promoted into the excited state by simultaneous absorption of two photons, showing the quadratic dependence on the incident photon flux is the number of photons involved in the TPA process, and A d, stands for the number of chromophores. More details are in the original reference [23]. 

Figure 1. The effect of near field stray radiation on the spectral line profile (546-nm Hg emission line). The detector was a microchannel-plate image intensified diode array (Reticon model RL-5I2SF, Princeton Instruments, Inc. model IRY-512). Key a, full line profile b, upper half (FWHM)ofline andc, lower portion of line, 0-10% relative emission...

Figure J. 23. Lorentzian, Doppler, and Voigt spectral line profiles for approximately equal half widths and intensities. (From Andrews et al.., 1987).

Measuring the Spectral Line Profile and Area Using Frequency Modulation... 

The linewidth broadening parameter may be incorporated into the response function derived by Baker et al. (their Equations 9 and 12). It relates the area under the spectral line profile Area, measured at 2o), to the spectroscopic parameters and the ratio m of Equation 6.2 above through a term 5 = (1 +... 

Fig. 1.53 Doppler-broadened absorption lines overlapping with the spectral line profile of a laser (a) level scheme and (b) line profiles...

Fig. 2.50 Spectral line profiles of the 1S-2S transition measured with Doppler-free two-photon excitation in an atomic hydrogen beam for different atomic velocities...

Particles in a liquid show a random velocity distribution with V(u = 1 mm/s. What is the spectral line profile of the beat signal, if the direct beam of a HeNe laser at A, = 630 nm and the laser light scattered by the moving particles is superimposed on the photocathode of the detector ... 

Dixon RN. 1986. The determination of the vector correlation between photo-fragment rotational and translational from the analysis of Doppler-broadened spectral line profiles . J. Chem. Phys. 85(4) 1866-1879. 

If the probability Pik(co) of absorption or emission of radiation with frequency CO causing a transition Ei -> Ek is equal for all the molecules of a sample that are in the same level ,, we call the spectral line profile of this... 

If the central plane of the near-confocal FPI is imaged by a lens onto a circular aperture with sufficiently small radius b < (Ar ) / only the central interference order is transmitted to the detector while all other orders are stopped. Because of the large radial dispersion for small p one obtains a high spectral resolving power. With this arrangement not only spectral line profiles but also the instrumental bandwidth can be measured, when an incident monochromatic wave (from a stabilized single-mode laser) is used. The mirror separation d = r - is varied by the small amount e and the power... 

The 300s oscillations have been mostly observed as velocity oscillations of 80+ 20m/s in photospheric spectral line profiles. Since they are not purely isothermal, they also appear as temperature fluctuations, and the comparison of phases between temperature and velocity can give indication on the propagation character of the waves. In the photosphere, the radiative relaxation time is of the order of Is and the wave is isothermal. 

If the probability Pjkico) of absorption or emission of radiation with frequency CO causing a transition , —Ek is equal for all the molecules of a sample that are in the same level Ei, we call the spectral line profile of this transition homogeneously broadened. Natural line broadening is an example that yields a homogeneous line profile. In this case, the probability for emission of light with frequency w on a transition , —> Ek with the normalized Lorentzian profile L co — coo) and central frequency coq is given by... 

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