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A practical procedure is described to measure photofragment μ-v-j correlations using polarized 1+n′ resonance-enhanced multiphoton ionization with a time-of-flight mass spectrometer detector. Following the theory of Dixon [R. N. Dixon, J. Chem. Phys. 85, 1866 (1986)], the correlations are expressed as the moments of a bipolar harmonic expansion of the correlated angular distribution of photofragment velocity and angular momentum (v and j) about the parent molecule transition dipole, μ. At a fixed detection geometry and on a single rotational transition, polarization control of the dissociating or probing light permits selective determination of targeted moments of the bipolar harmonic expansion. The velocity-dependent spherical tensor moments of the angular momentum distribution depend upon these bipolar moments and are given for a general experimental geometry and for general elliptical polarization of the probing light. Several practical experimental geometries are described that isolate and measure targeted bipolar moments. The bipolar moments that can be measured using elliptical probe polarizations are described. A method for analyzing the symmetries of dissociation dynamics is proposed and used to identify the moments unique to the dynamics of chiral systems.

The Li 2 species offers an ideal system to compare experimental pump/probe ultrafast photoionization with quantum dynamical calculations on well characterized potential energy surfaces. The present work utilizes the best available potential energy surfaces and appropriate quantum dynamical methods to analyze the photoionization and dynamics of a wave packet prepared in the E 1 ⌺ g ϩ shelf state of lithium dimer. A direct comparison between calculated ͑ab initio͒ and measured quantum dynamics is made for signals obtained with different laser pulse shapes, intensities, and chirps, and the validity of the theoretical model is considered, as well as the applicability and failure of perturbation theory. The results illustrate the high sensitivity of the time-dependent pump/probe ionization transient signals to the detailed modeling of both the pump and probe stages. They also show some of the inadequacies of the current potential surfaces and dipole moment matrix elements of lithium dimer.