Laser-initiated isomerization in H-bonded solute-solvent complexes

PHYS 74

Timothy S. Zwier, zwier@purdue.edu, Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084
Often solute-solvent complexes are formed in a supersonic expansion in two or more distinct isomeric structures. Using the recently-developed method of stimulated emission pumping-population transfer spectroscopy, it is possible to selectively excite one of these isomers and to vary its internal energy systematically. When the energy barrier to isomerization between the structures is overcome, isomerization can occur, and the population can be trapped in the other well for spectroscopic interrogation. We will report results on four ‘solvent isomerization' reactions in which we probe (i) the effect of a complexed water molecule on the barrier to isomerization of a flexible solvent, (ii) the barrier for shuttling a single water molecule between remote H-bonding sites on trans-formanilide, (iii) the barrier to motion from one lone pair to another in an OH…O H-bond, and (iv) excitation of the phenol solvent is used to isomerize the H-bonded solvent.