Resonance broadening velocity

For suitable substances the average life-time of the hydrated or unhydrated species can be deduced from the broadening of nuclear magnetic resonance lines. This has recently been applied to acetaldehyde (Evans et al., 1965 Ahrens and Strehlow, 1965) and to isobuty-raldehyde (Hine and Houston, 1965) the velocities deduced for catalysis by hydrogen ions are in fair agreement with those obtained by other methods. 

On the other hand, increasing 2 has the disadvantage of broadening and shifting the resonance peaks as shown below. Photons emitted at an angle 0 with respect to the direction of the Doppler velocity, will leave the source with an energy E, given by (30, 32,114)... 

Demonstration of levitation of micron-sized latex particles by radiation pressure dates back to 1970 in the experiments reported by Ashkin [Ashkin 1970]. The average force accelerating (or slowing down) atoms in a laser field was derived by A.Kazantsev in 1972 [Kazantsev 1974]. Later in 1972-1974 he classified the optical forces as spontaneous, induced and mixed. In particular, it was he who first presented the dipole potentials for velocity broadened lines of resonance atoms in the logarithmic form... 

The slow rotational diffusion of the particles leads to a certain broadening of resonance lines and side bands (Fig. 10), finally resulting in a total loss of the MAS effect when the correlation time r reaches the same order of magnitude as the reciprocal spinning velocity 1/cUr (Fig. 10, bottom). The sideband integrals follow a pattern which is predicted by the method of Herzfeld and Berger." ... 

X 10 for up to 202 mms for Re. They are all very small when compared with the tremendous velocities ( 7 x 10 mm s ) used by Moon in 1950 to detect nuclear resonance fluorescence without recoilless emission, and show dramatically that the Mossbauer technique eUminates both recoil and thermal broadening. The Heisenberg relation means that an excited state with a shorter half-life has a greater uncertainty in the y-transition energy and hence a broader resonance line. 

The reaction rate of a moderated uranium pile depends on temperature. For example, in a reactor in which the neutron spectrum is approximately Maxwellian, the average velocity will increase with temperature, thus decreasing the absorption cross sections for the low-energy neutrons which vary as 1/v. Resonance levels will be broadened by the Doppler effect, and if lumping of the uranium has been made use of to decrease the total resonance absorption as proposed by Szilard, and later found experimentally to be effective, increased temperature will decrease the advantage thus gained. 

The problem of transit-time broadening was recognized many years ago in electric or magnetic resonance spectroscopy in molecular beams [1253]. In these Rabi experiments [1254], the natural linewidth of the radio frequency or microwave transitions is extremely small because the spontaneous transition probability is, according to Vol. 1, (2.22), proportional to co. The spectral widths of the microwave or RF lines are therefore determined mainly by the transit time AT = d/v of molecules with the mean velocity v through the interaction zone in the C field (Fig. 5.10a) with length d. 

Only collisions with Av = Av k = Av Xcos > XAvs bring the molecules out of resonance with the laser line. Collisions with An < XAvs only redistribute the velocities and do not contribute essentially to the line broadening. The cross section for these collisions with Av > XAvj is [Pg.674]

In this contribution we present two laser spectroscopic methods that use coherent resonance Raman scattering to detect rf-or laser -induced Hertzian coherence phenomena in the gas phase these novel coherent double resonance techniques for optical heterodyne detection of sublevel coherence clearly extend the above mentioned previous methods using incoherent light sources. In the case of Doppler broadened optical transitions new signal features appear as a result of velocity-selective optical excitation caused by the narrow-bandwidth laser. We especially analyze the potential and the limitations of the new detection schemes for the study of collision effects in double resonance spectroscopy. In particular, the effect of collisional velocity changes on the Hertzian resonances will be investigated. 

Fig. 4. Pressure dependence of rf resonance linewidths (HWHM) of AM- and FM-Raman heterodyne signals for xenon and helium collision partners. Experimental points are given by crosses the full curves correspond to fits that are based on a theory including velocity diffusion processes. Dashed lines, initial slopes for the AM-RHS pressure broadening giving YvcC dash-dotted lines, asymptotic slopes for FM-RHS linewidths giving Yc-...

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