Dynamics of harpooning studied by transition state spectroscopy - Part III. Li center dot center dot FCH (3)

The Van der Waals complex Li . . . FCH3 has been formed in a crossed molecu lar beam apparatus. The transition state (TS) for the reaction Li*(2p P-2) + FCH3 --> LiF + CH3 was accessed at various configurations by laser-excita tion of the complex by Li . . . FCH3 complex by tunable visible radiation, lambda (1). Photoinduced depletion of the complex by excitation to this TS was found to occur across a broad range of lambda (1) from 570 to 850 nm. T his 'action spectrum' consisted of two broad regions located to either side of the atomic transition line of Li (2p P-2 <-- 2s S-2). The first region, between 700 and 850 nm, was dominated by sharp maxima in the depletion int ensity. A broad peak with weakly-resolved structure characterized the secon d region, between 570 and 680 nm. These findings were interpreted by means of high-level ab initio calculations of the potential-energy surfaces in th e TS region. The peaks in the photodepletion spectrum were assigned to spec ific electronic transitions, their shapes and intensities being explained i n terms of calculated transition-dipole moments and rovibrational wavefunct ions.