photoinduced processes in which vibrational coherences are detected on the ground
state potentials [23].
The observation of peaks in all four quadrants in Fig. 10c confirms that the
process of interest has been isolated (i.e., the pathway defined in Fig. 1). We find
that Fourier transforming the signal with respect to only s 2 facilitates signal
interpretation (see Fig. 11a) [23]. In this representation, oscillations of the signal in
s 1 represent recurrences of a vibrational wave packet on the ground state potential
energy surface of the triiodide reactant, whereas the vibrational spectrum of diiodide
is displayed in x 2 . The average vibrational frequency of diiodide is computed at
each delay point using
x vib s 1
ð Þ
h
i¼
R
dx 2 S s 1 ; x 2
ð
Þx 2
R
dx 2 S s 1 ; x 2
ð
Þ
;
ð6Þ
where S(s 1 , x 2 ) represents the absolute value of the signal displayed in Fig. 11a.
The recurrences in hx vib (s 1 )i shown in Fig. 11b indicate that the frequency of wave
packet motion of diiodide depends on the geometry of the triiodide at the ‘‘instant’’
the reaction is initiated by the repump laser pulse. Notably, this analysis is insensitive to the signal phase because it is carried out on the absolute value of the signal.
Based on earlier work [37], we suggest that the non-equilibrium distribution of
vibrational quanta in the diiodide product governs the vibrational coherence frequency of this anharmonic system.
Further insight is obtained by converting the delay time, s 1 , into the classical
bond length of triiodide. This calculation makes use of the equilibrium bond length,
the electronic dephasing time, the vibrational period of the symmetric stretching
vibration, and the London–Eyring–Polanyi–Sato excited state potential energy
surface of triiodide in ethanol [36, 45]. A classical view of the wave packet is
justified by heterogeneity of the molecular geometry in the condensed phase
environment. Wave packet dynamics can often be successfully described by solving
Fig. 11 a Fourier transforming the 2DRR signal with respect to only s 2 reveals quantum beats of
triiodide in the delay time, s 1 . b The average vibrational frequency of diiodide is computed at each delay
point using the signal displayed in panel (a). c The delay, s 1 , is translated into the bond lengths of
triiodide. The diagonal slant of the spiral suggests that a bond length displacement of 0.1 A ˚ in triiodide
induces a shift of approximately 6.8 cm
-1 in the vibrational coherence frequency of diiodide Adapted
from Guo et al. [23], with the permission of AIP Publishing
Top Curr Chem (Z) (2017) 375:87
123
264
Reprinted from the journal
state potentials [23].
The observation of peaks in all four quadrants in Fig. 10c confirms that the
process of interest has been isolated (i.e., the pathway defined in Fig. 1). We find
that Fourier transforming the signal with respect to only s 2 facilitates signal
interpretation (see Fig. 11a) [23]. In this representation, oscillations of the signal in
s 1 represent recurrences of a vibrational wave packet on the ground state potential
energy surface of the triiodide reactant, whereas the vibrational spectrum of diiodide
is displayed in x 2 . The average vibrational frequency of diiodide is computed at
each delay point using
x vib s 1
ð Þ
h
i¼
R
dx 2 S s 1 ; x 2
ð
Þx 2
R
dx 2 S s 1 ; x 2
ð
Þ
;
ð6Þ
where S(s 1 , x 2 ) represents the absolute value of the signal displayed in Fig. 11a.
The recurrences in hx vib (s 1 )i shown in Fig. 11b indicate that the frequency of wave
packet motion of diiodide depends on the geometry of the triiodide at the ‘‘instant’’
the reaction is initiated by the repump laser pulse. Notably, this analysis is insensitive to the signal phase because it is carried out on the absolute value of the signal.
Based on earlier work [37], we suggest that the non-equilibrium distribution of
vibrational quanta in the diiodide product governs the vibrational coherence frequency of this anharmonic system.
Further insight is obtained by converting the delay time, s 1 , into the classical
bond length of triiodide. This calculation makes use of the equilibrium bond length,
the electronic dephasing time, the vibrational period of the symmetric stretching
vibration, and the London–Eyring–Polanyi–Sato excited state potential energy
surface of triiodide in ethanol [36, 45]. A classical view of the wave packet is
justified by heterogeneity of the molecular geometry in the condensed phase
environment. Wave packet dynamics can often be successfully described by solving
Fig. 11 a Fourier transforming the 2DRR signal with respect to only s 2 reveals quantum beats of
triiodide in the delay time, s 1 . b The average vibrational frequency of diiodide is computed at each delay
point using the signal displayed in panel (a). c The delay, s 1 , is translated into the bond lengths of
triiodide. The diagonal slant of the spiral suggests that a bond length displacement of 0.1 A ˚ in triiodide
induces a shift of approximately 6.8 cm
-1 in the vibrational coherence frequency of diiodide Adapted
from Guo et al. [23], with the permission of AIP Publishing
Top Curr Chem (Z) (2017) 375:87
123
264
Reprinted from the journal