Rm. Stratt et M. Maroncelli, NONREACTIVE DYNAMICS IN SOLUTION - THE EMERGING MOLECULAR VIEW OF SOLVATION DYNAMICS AND VIBRATIONAL-RELAXATION, Journal of physical chemistry, 100(31), 1996, pp. 12981-12996
Two of the more fundamental ways in which molecules change their behav
ior when they are dissolved are that they can begin to exchange energy
with the surrounding liquid and they can induce their surroundings to
rearrange so as to provide a significant stabilizing influence. The f
irst of these is typified by the process of vibrational population rel
axation of a vibrationally hot species. The second concept-critical to
solution chemistry-is what is known as solvation. Both of these proce
sses are sufficiently fundamental that one would really like to know,
at the most mechanical and molecular level possible, just what events
are required in order to make them happen. But how difficult is it goi
ng to be to extract such molecular detail from the complicated many-bo
dy dynamics? The most microscopic level of understanding one could eve
r hope to possess might seem far removed from the finely detailed dyna
mical information which is available routinely for individual isolated
molecules and for molecule-molecule collisions in molecular beams. It
might even seem that the broad, almost featureless character of typic
al solute spectra would condemn us to never being able to measure anyt
hing more than a few paultry tidbits of highly averaged data caricatur
ing the intriguing processes that can take place in liquids. However,
spectroscopists have for some time been able to infer at least some as
pects of the dynamics of liquids from the spectroscopy of dissolved mo
lecules, and with the advent of novel ultrafast time-resolved spectros
copies and new theoretical perspectives, the likelihood of resolving s
olution dynamics into genuinely molecular components has increased dra
matically. We discuss a few of these recent developments here for the
special, but nonetheless illuminating, cases of solvation dynamics and
vibrational relaxation and note a few of the more promising direction
s that future work might take.