Short-time solvation dynamics probed by phase-locked heterodyne detected pump-probe

Abstract

Phase-locked heterodyne detected pump-probe experiments are reported on solutions of a dye molecule in ethylene glycol, methanol and acetonitrile. By performing experiments at different phase-lock wavelengths, the real and imaginary parts of the line broadening function g(t) could be mapped out. The imaginary part of g(t) is directly related to dissipative dynamics. Comparison of the experimental data with calculations based on the Brownian oscillator model yields soivation frequencies that are substantial higher than those reported using MD simulations on similar systems.

Multidimensional Femtosecond Correlation Spectroscopies of Electronic and Vibrational Excitations

“…The heterodyne-detection ͑time-gated͒ mode which involves mixing the signal with an additional heterodyne pulse, yields the time resolved signal and also maintains the information about its phase. 3,6,7,50,51 In femtosecond twodimensional ͑2D͒ four-wave mixing spectroscopy, two of the three pulses are time-coincident and only differ by their wave vector. The system thus interacts once with one pulse and twice with a pulse pair.…”

All-solid-state cavity-dumped sub-5-fs laser

“…Of course, the technical demands made on a 5-fs autocorrelator are substantial. In our experiments we employ a Mach-Zehnder interferometer [50,[109][110][111], which has the advantage of being fully symmetric with respect to both arms. Note that the "magic" 0 : 1 : 8 ratio between the minimum, asymptotic level, and maximum of the IAC trace [108] is obtained only if the intensities of the two interfering beams are strictly equal.…”

Mode suppression in the non-Markovian limit by time-gated stimulated photon echo

“…The fact that the integrated echo signal ͑the left panel͒ exhibits no signature of mode suppression proves, however, that the system dynamics is non-Markovian. 34 Of course, this had been established before, most notably by the finding of an imaginary component in g(t), 40 which cannot occur in the Bloch model. The observed exponential decay of the time-gated echo for t 13 ϭ210 fs thus necessitates the presence of an ultrafast nonMarkovian process, whose correlation time is ϳ20 fs ͓Eq.…”

“…These slow dynamical processes lead to inhomogeneous broadening of the optical transition on a time scale of less than 1 ps. Recently performed phase-locked pump-probe measurements 40 show that the fastest solvation event in DTTCI in ethylene glycol occurs in about 50 fs. This initial ultrafast process does not manifest itself in echo shift measurements, probably because it occurs in the time window where the excitation pulses overlap in time.…”

“…This conclusion accords with recent phase-locked pump-probe experiments which provide a correlation time of ϳ50 fs for this system. 40 For longer delays of the third pulse, the time-gated echo decays become increasingly faster. The reason for this behavior is threefold: First, solvent modes that could be considered inhomogeneous for short waiting times t 13 ͑Table I͒ do affect the echo decay now.…”