PRACTICAL ASPECTS OF ALIGNING ASYMMETRIC-TOP MOLECULES VIA SINGLE-PHOTON EXCITATION - AN APPLICATION TO S-1[-S-0 EXCITATION OF GLYOXAL

The practical aspects of aligning glyoxal (CHO-CHO) via S-1 <-- S-0 ph otoexcitation with a linearly polarized laser are considered, with an emphasis on preparing the aligned molecules to probe for steric effect s in crossed beam energy transfer, The degree to which ''broadside'' a nd ''edge-on'' collision geometries can be obtained for the planar gly oxal molecule is quantified. For a pump laser polarization parallel to the relative collision velocity, an aligned distribution is predicted in which a broadside collision is 2.3 times more likely than an edge- on collision. For the perpendicular laser polarization, an edge-on col lision is 1.6 times more likely than a broadside collision, Implementa tion of alignment via photoexcitation in an actual experiment is descr ibed. Concerns when aligning molecules via this method are discussed, including saturation effects and nuclear spin depolarization. The lase r-induced fluorescence formalism of Greene and Zare [J. Chem. Phys. 19 83, 75, 6741] is used to demonstrate that glyoxal call indeed be align ed to the degree predicted by theory.