Laser and Coherence SpectroscopyJeffrey I. Steinfeld The impact which has been made on spectroscopy by lasers, and by this route on major segments of physics and chemistry, has received ample documen tation in the past several years. Two principal themes emerge from examina tion of the numerous books and monographs now available on this subject: first, an increase in spectral resolution to levels previously undreamed of; and, second, the generation of nonlinear phenomena as a result of the intense radiation fields available from laser devices. There is one additional property of laser radiation which, although used extensively in experiments, does not appear to have been as thoroughly reviewed as the foregoing aspects. This is the spatial and temporal coherence of the radiation field produced by the laser, which makes possible the coherent excitation of molecular energy states. This feature is the subject of the present volume. While the use of coherence methods in spectroscopy has been paced by lasers, it is by no me ans restricted to this technology. In the second and fourth chapters, microwave sources are discussed as generators of coherent radiation fields and are used to probe both rotational energy levels and spin states of electronically excited molecules. The phenomena discussed in this book, such as nutation, free induction decay, radiative echoes, rapid pas sage, and so forth, are really the same in different regions of the spectrum, and themselves echo from one chapter to the next. |
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amplitude atoms average axis beam Bloch equations calculation Chem CO2 laser collisional components delayed nutation density matrix dephasing detector discussed Doppler Doppler broadening double-resonance doublet dye laser echo experiment electronic emitted excited exponential fluorescence free induction decay function infrared initial conditions integral intensity interaction Lett linewidth matrix elements measure microwave microwave spectroscopy molecular molecules nutation observed obtained off-resonance optical Bloch equations optical field optical nutation phase photon photon echo Phys polarization population matrix precess probe processes pulse sequence pumping quantum radiation Raman Raman scattering relaxation result rotational sample scattering second pulse Section shown in Figure solution spectral spectroscopy spectrum spin spontaneous emission Stark field Stark switching steady-state stimulated echo sweep T₁ T₂ technique tion transient effects transition two-level system two-pulse echo v₂ VC collisions velocity group vibrational width zero