to the energized products as they emerge from
the TS and displacement of the TS later along the
reaction coordinate. Equilibration of the excess
DF vibrational energy takes 3 to 4 ps in both
solvents. Further solvent restructuring to accom-
modate reaction products continues over the
ensuing 10 ps. This depth of understanding of a
condensed-phase reaction mechanism requires
knowledge not only of the PES but also of the
dynamical interplay between solute and solvent.
Vibrational probes of reactions in solution and
nonequilibrium MD simulations provide pen-
etrating insights into the dynamics of bond-
making and subsequent dissipation of excess
chemical energy to the solvent. Further explora-
tion using this combined methodology will pro-
vide increasingly detailed descriptions of the
effect of emergent product vibrational excitation
on reaction outcomes in complex systems.
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The Bristol group thanks the Engineering and Physical Sciences
Research Council (EPSRC, Programme Grant EP/G00224X and
a studentship for G. T.D.) and the European Research Council
(ERC, Advanced Grant 290966 CAPRI) for financial support. D.R.G.
acknowledges award of a Royal Society University Research
fellowship, J.N.H. acknowledges a Royal Society Wolfson Merit
Award, and S.J.G. thanks EPSRC for award of a Career Acceleration
Fellowship (EPSRC EP/J002534/2). Experimental measurements
were conducted at the ULTRA Laser Facility, which is supported
by the Science and Technology Facilities Council (STFC, Facility
Grant ST/501784). We are grateful to F. Abou-Chahine for
assistance with collection of some of the experimental data and
to M. P. Grubb and M. N. R. Ashfold for valuable discussions.
All experimental data and analysis files are archived in the
University of Bristol’s Research Data Storage Facility. The
supplementary materials contain summaries of the data analysis
procedures and outcomes. Individual contributions to the work:
A.J.O.-E. and G. T.D. devised and carried out the experiments,
with assistance from S.J.G., and analyzed the experimental data
with T.J.P. and S.J.G. G.M.G., I.P.C., and M. T. constructed and
operated the ultrafast laser system at the Central Laser Facility,
with which all experimental data were collected. D.R.G. and
J.N.H. devised and performed the MD simulations and analyzed
the computational results. A.J.O.-E., G. T.D., T.J.P., D.R.G., and
J.N.H. wrote the paper.
Materials and Methods
Figs. S1 to S7
Tables S1 to S2
8 October 2014; accepted 29 December 2014
Fig. 3. Transient DF vibrational energy content following D-atom abstractions in d3-acetonitrile,
obtained from the MD simulations. (A) DF vibrational energy averaged over 200 trajectories, with time
constants obtained from a biexponential fit. (B1 to B4) Normalized transient vibrational energy content in
the n = 0 to 3 vibrational levels. Exponential fits to the decaying populations of n = 3, 2, and 1 and the rise in
n = 0 give time constants of t3→2 = 0.37 T 0.20 ps, t2→1 = 3.6 T 1.8 ps, and t1→0 = 6.9 T 1.4 ps.
Fig. 4. MD simulations of transient power spectra and radial distribution functions. (A) Transient
DF spectral bands (black lines), Gaussian fits to the simulated DF spectra (red lines), and the simulated
solvent spectrum (gray lines). (B) Time-dependent postreaction profile of the DF band center (circles),
together with results from separate simulations that identify spectral effects of hydrogen-bond formation
with CD3CN (dotted line) and relaxation of vibrationally excited DF (dashed line). (C) Time evolution of the
radial distribution function, g(r), which describes the changing distribution of distances of the D atom (in
DF) to the N atoms of the CD3CN solvent molecules.