Knowledge Bank

The spectral manifestation of complicated intramolecular dynamics of larger molecules is the presence of numerous local perturbations in the spectrum. A fully resolved spectrum in this case provides a wealth of information about the details of the dynamics. However, in order to interpret the spectrum it is first necessary to assign all approximately good quantum numbers so that truly homogeneous information is available. We have recently applied quadrupole state focussing techniques to study these complex spectra. Molecules with complex spectra show a simplifying behavior: they are not deflected by the inhomogeneous electric field. The result is that enhanced sensitivity can be gained due to the different spatial collection characteristics of vibrationally excited and ground state molecules. The lack of deflection of the vibrationally excited molecules also ensures that the dynamical information contained in the relative intensities is preserved. Double-resonance geometries can be chosen that allow assignment of these spectra at the full sensitivity of the single-photon spectrum. Since these double-resonance arrangements depend mostly on the different collection properties of two ground rotational levels it is only necessary to be able to saturate the ground state rotational transitions.