Schematic energy level diagram in VER of Bz2 and a pump-probe excitation scheme. In this figure, energy difference between S0, S1, and IP for (Bz)2 and Bz as well as the dissociation energy in neutral and ionic states are embedded with cm−1 unit. The values are taken from Ref. 67.
(a): IR spectrum of benzene monomer measured by a nanosecond laser system. (b)-(c): IR spectra obtained by monitoring hd + and hh + mass channels, respectively, with a picosecond laser system. Arrows show the IR excitation energy used for the pump-probe experiment.
Transient UV spectra at Δt = +30 (black), +100 (red), and +300 ps (blue) observed with the IR excitations fixed at each Fermi band (bands a, b, and c). Green ones are UV spectra measured without IR excitation. The UV spectra (a) and (b) are obtained by monitoring hd + and hh + mass channels, respectively. In panel (c), UV power is plotted. Arrows show the UV energy used for the observation of time profiles.
Decay time profiles measured by monitoring hd + and hh + mass channels after the IR excitation at bands b and c. Two decay profiles in each panel were observed at different probe UV frequencies. Red curves correspond to the single-exponential decay function convoluted with the IR and UV Gaussian pulses. The best decay lifetimes are embedded in this figure.
Vector motions of CH stretching vibration (ν20) of tilted benzene dimer (C s) calculated at ωB97X-D/6-311++G(3df, 2p) level of theory.
Time evolutions probed with three different UV energies after the IR excitation of bands a and b. These were observed by monitoring (a) hd + and (b) hh + mass channels. Red curves are fitted by using Eq. (2) with τ2 = 400 and τvp = 4000 ps. The used τ1 values correspond to 140 ps for band b. For τ1 of band a, 150 and 130 ps are used for the hd and hh dimers, respectively. Blue and green curves represent bath1 and bath2 components, respectively, in each red curve (see text).
(a): Time evolutions obtained by monitoring h + and hd + mass channels with the 37 800 cm−1 UV pulse after the IR excitation of band a. (b): A difference time profile subtracting the hd + time profile from the h + one. Red curve is obtained by a fitting with τ1 = 140, τ2 = 400, and τvp = 4000 ps.
Time profiles of VER of Bz3 obtained by monitoring dd + signal. Red lines are obtained by fitting with τ1 = 50, τ2 = 300, and τvp = 1000 ps. Blue and green solid lines correspond to bath1 and bath2 time evolutions, respectively.
Time constants (ps) on vibrational energy relaxation of benzene dimer and trimer after the IR excitation of the Fermi polyads (band a b, and c) of the CH stretching vibration.
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