“…33 This functional yields good results for excited states, 34 noncovalent interactions, and ion pairs. 35,36 Our optimized structures for neutral (FA) n (n < 5) agree with previous results, preferring dimer pairs linked by hydrogen bonds. 37,38 Although several structures are possible for larger clusters, 39 bulk FA crystallizes in similar planar catameric chains, with H-bonds linking each neighbor.…”
The ultrafast proton transfer dynamics
of homogeneous
formic acid
clusters (FA)
n
, n <
10, are investigated with femtosecond time-resolved mass spectrometry.
We monitor the proton transfer pathway following Rydberg state electronic
relaxation and find that successful ion pair formation increases logarithmically
with cluster size. Ab initio calculations demonstrate similar excitation/relaxation
behavior for each cluster, revealing a contact ion pair forms between
two molecules composing the cluster before finally a formate anion
(HCOO−) is dissociated by the probe pulse. The sub–ps
time scale for rearrangement and proton transfer increases almost
linearly with cluster size, requiring ∼67 fs per additional
formic acid molecule and ranging from 213 ± 51 fs for the trimer
to 667 ± 116 fs for FA9. The near-linear trends measured
for both rearrangement lifetime and ion pair formation suggest that
proton transfer is unlikely in the formic acid dimer but becomes prominent
in small clusters.
“…33 This functional yields good results for excited states, 34 noncovalent interactions, and ion pairs. 35,36 Our optimized structures for neutral (FA) n (n < 5) agree with previous results, preferring dimer pairs linked by hydrogen bonds. 37,38 Although several structures are possible for larger clusters, 39 bulk FA crystallizes in similar planar catameric chains, with H-bonds linking each neighbor.…”
The ultrafast proton transfer dynamics
of homogeneous
formic acid
clusters (FA)
n
, n <
10, are investigated with femtosecond time-resolved mass spectrometry.
We monitor the proton transfer pathway following Rydberg state electronic
relaxation and find that successful ion pair formation increases logarithmically
with cluster size. Ab initio calculations demonstrate similar excitation/relaxation
behavior for each cluster, revealing a contact ion pair forms between
two molecules composing the cluster before finally a formate anion
(HCOO−) is dissociated by the probe pulse. The sub–ps
time scale for rearrangement and proton transfer increases almost
linearly with cluster size, requiring ∼67 fs per additional
formic acid molecule and ranging from 213 ± 51 fs for the trimer
to 667 ± 116 fs for FA9. The near-linear trends measured
for both rearrangement lifetime and ion pair formation suggest that
proton transfer is unlikely in the formic acid dimer but becomes prominent
in small clusters.
“…This would result in the total KER of around 8.4 eV (3 × 1/R) as each benzene molecule in the trimer is in direct interaction with the other two benzene molecules. This value lies about 1.0 eV higher than the measured KER, indicating that some amount of the Coulomb repulsion energy might be transferred to the rotational and vibrational motions of the molecular ions 53 , 54 . Fig.…”
Intermolecular interactions involving aromatic rings are ubiquitous in biochemistry and they govern the properties of many organic materials. Nevertheless, our understanding of the structures and dynamics of aromatic clusters remains incomplete, in particular for systems beyond the dimers, despite their high presence in many macromolecular systems such as DNA and proteins. Here, we study the fragmentation dynamics of benzene trimer that represents a prototype of higher-order aromatic clusters. The trimers are initially ionized by electron-collision with the creation of a deep-lying carbon 2s−1 state or one outer-valence and one inner-valence vacancies at two separate molecules. The system can thus relax via ultrafast intermolecular decay mechanisms, leading to the formation of C$${}_{6}{{{{{{{{{\rm{H}}}}}}}}}_{6}}^{+}\cdot$$
6
H
6
+
⋅
C$${}_{6}{{{{{{{{{\rm{H}}}}}}}}}_{6}}^{+}\cdot$$
6
H
6
+
⋅
C$${}_{6}{{{{{{{{{\rm{H}}}}}}}}}_{6}}^{+}$$
6
H
6
+
trications and followed by a concerted three-body Coulomb explosion. Triple-coincidence ion momentum spectroscopy, accompanied by ab-initio calculations and further supported by strong-field laser experiments, allows us to elucidate the details on the fragmentation dynamics of benzene trimers.
“…Here, we calculate the diffusion coefficient via a classical method instead of an accurate quantum treatment method such as ab initio molecular dynamics. 37,38 Through fitting the mean square displacement (MSD) using the relation 〈| r ( t ) − r (0)| 2 〉 = 4 D act t , we plotted the values of diffusion coefficient D act in Fig. 5 where two examples of MSD with A p = 0.3 and A p = 0.8 are shown in the inset.…”
The dynamics of self-propelled micro-motors, in a thin fluid film containing an attractive substrate, is investigated by means of a particle-based simulation. A chemically powered sphere dimer, consisting of a...
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