Abstract
AbstractFemtosecond time‐resolved rotational coherence spectroscopy (RCS), when applied in a Raman scattering version, can be utilized for the measurement of highly accurate rotational and centrifugal constants of ground and vibrationally excited states of nonpolar molecules. A brief outline of the theoretical background is given, including the basics of rotational coherence spectroscopy, nonlinear optical four‐wave mixing (FWM), molecular polarizability, the rotational Raman process, nuclear spin statistics, and collisional dephasing. An experimental setup for femtosecond rotational Raman RCS measurements is described, featuring some of the points necessary to achieve high experimental accuracy. Rotational Raman RCS spectroscopy has been performed on a number of nonpolar linear and symmetric‐top molecules. The examples presented here (CS2, cyclobutane, and cyclooctatetraene) are selected to show the scope of the method and currently achievable accuracy of the rotational and the centrifugal distortion constants, as well as the detailed considerations necessary to achieve these results. The last section reviews a procedure for the determination of semiexperimental equilibrium structures.
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