Ethanol Glass Dynamics:  Logarithmic Line Broadening and Optically Induced Dephasing

Abstract

The time and fluence dependence of the homogeneous line width of Zn-porphin in deuterated ethanol glass at 1.8 K is remeasured by stimulated photon echo. The observed spectral dynamics is interpreted in terms of the standard two-level system model and by using a commonly used modified version of it. It is shown, as was suggested recently (Phys. ReV. B 1997, 56, 11571), that time-dependent local heating is the cause of the plateau found in earlier echo experiments on this system. The anomalous intensity loss of the photon echo in the population dimension, however, is confirmed, as well as the existence of excess optical dephasing on a short time scale. The former effect is attributed to spontaneous frequency jumps outside the laser bandwidth, the latter to spectral diffusion induced by the change of electronic state of the chromophore. This phenomenon is not captured in existing theoretical models, which assume the probe molecule to be just a spectator of glass dynamics.

Solvent dynamics in a glass-forming liquid from 300K to 3K: What photon echoes can teach us

“…Also, the repetition rate was kept at 10 kHz. At these pulse energies an estimate suggests that transient temperature effects play no role in our experiments [73,74]. Notwithstanding the low pulse energies, at temperatures below 80 K and right above the glass temperature (at 150 K, see below), where the heat capacity of the sample was small, some bleaching occurred over the time scale of several scans ( 1 2 hour).…”

“…Whereas at 300 K the echo is approximately 40 fs wide, at 3 K this has become ffi80 fs at FWHM. The echo maximum shifts from nearly 9 fs at room temperature to over 22 fs at 3 K. Although the echo stretches to longer times at lower temperatures, the nanosecond decays observed in the experiments with picosecond pulses are not present here [28,74].…”

Dissymmetries in fluorescence excitation and emission from single chiral molecules

“…Using single‐molecule imaging techniques, researchers are now able to explore, with unprecedented clarity, details of individual molecular behavior, structure, and the coupling with local environment. The advent of ultrahigh precision time‐to‐digital converters, photon‐counting avalanche photodiodes, and enhanced‐sensitivity/high‐ speed charge‐coupled device (CCD) imaging detectors coupled with high‐numerical aperture microscopy platforms now provide access to a number of single‐molecule fluorescence observables such as fluorescence lifetime,60, 144, 148–150 “blinking” behavior,151–163 spectral and spatial diffusion,143, 158, 164–192 and polarization anisotropy 149, 150, 193–201. In recent years, important new methodologies in single‐molecule imaging have emerged including sub‐diffraction limit spatial imaging, integration of scanning probe microscopies with fluorescence probes, multi‐photon imaging, fluorescence resonant energy transfer (FRET), and molecular orientation determination by defocused emission pattern measurements 202–214.…”