In this paper we present a tensor analysis of Raman induced polarization spectroscopy (RIPS), a variation of time-resolved rotational coherence spectroscopy (RCS), developed in our laboratory to study coherent rotational motions in fluids over a range of densities. Based on the irreducible tensor algebra, the analysis separates the fundamental molecular response in RIPS from the dependence of the signal on geometric factors (i.e., laser polarizations). Explicit formulas for the femtosecond RIPS response of symmetric and asymmetric tops are derived. The results are in good agreement with experimental RIPS spectra of low pressure CO2 and O3. The tensor analysis is also generalized to other types of four wave mixing experiments, allowing detailed comparison of the various frequency- and time-domain pump–probe experiments.
Femtosecond time-resolved multiphoton ionization spectroscopy is applied to the study of the photodissociation of OClO. The observed ratio of O2+/ClO+ signal increases 12-fold with a 3-fold increase of the pump laser intensity. They are attributed to the change in the branching ratio between the two independent reaction channels leading to Cl+O2 and ClO+O, respectively. We believe this is the first experimental demonstration of laser controlled chemical reactions by femtosecond ponderomotive forces. At low pump power, the photodissociation dynamics at 386 nm is shown to be a two-step process, with the OClO slowly approaching (time constant 4.6 ps) a transition state that falls apart rapidly (time constant 250 fs).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.